Use django-djconfig for kfet app.

Old configuration(/settings), based on Settings model, system is
deleted: SettingsForm, Settings.
New system use `django-djconfig` module.

- `kfet.config` module provides `kfet_config` to access configuration concerning
kfet app.
- Views, forms, models, etc now use this object to retrieve conf values.
- Views no longer add config values to context, instead templates use
  `kfet_config` provided by a new context_processor.
- Enhance list and update views of settings.
- Fix: settings can directly be used without having to visit a specific
  page...

Misc
- Delete some py2/3 imports
- Delete unused imports in kfet.models and kfet.views
- Some PEP8 compliance

kfet/models.py

@@ -1,12 +1,7 @@
 # -*- coding: utf-8 -*-
 
-from __future__ import (absolute_import, division,
-                        print_function, unicode_literals)
-from builtins import *
-
 from django.db import models
 from django.core.urlresolvers import reverse
-from django.core.exceptions import PermissionDenied, ValidationError
 from django.core.validators import RegexValidator
 from django.contrib.auth.models import User
 from gestioncof.models import CofProfile
@@ -15,11 +10,12 @@ from django.utils import timezone
 from django.utils.encoding import python_2_unicode_compatible
 from django.db import transaction
 from django.db.models import F
-from django.core.cache import cache
-from datetime import date, timedelta
+from datetime import date
 import re
 import hashlib
 
+from kfet.config import kfet_config
+
 def choices_length(choices):
     return reduce(lambda m, choice: max(m, len(choice[0])), choices, 0)
 
@@ -113,8 +109,8 @@ class Account(models.Model):
         return data
 
     def perms_to_perform_operation(self, amount):
-        overdraft_duration_max = Settings.OVERDRAFT_DURATION()
-        overdraft_amount_max = Settings.OVERDRAFT_AMOUNT()
+        overdraft_duration_max = kfet_config.overdraft_duration
+        overdraft_amount_max = kfet_config.overdraft_amount
         perms = set()
         stop_ope = False
         # Checking is cash account
@@ -620,116 +616,6 @@ class GlobalPermissions(models.Model):
             ('special_add_account', "Créer un compte avec une balance initiale")
         )
 
-class Settings(models.Model):
-    name = models.CharField(
-        max_length = 45,
-        unique = True,
-        db_index = True)
-    value_decimal = models.DecimalField(
-        max_digits = 6, decimal_places = 2,
-        blank = True, null = True, default = None)
-    value_account = models.ForeignKey(
-        Account, on_delete = models.PROTECT,
-        blank = True, null = True, default = None)
-    value_duration = models.DurationField(
-        blank = True, null = True, default = None)
-
-    @staticmethod
-    def setting_inst(name):
-        return Settings.objects.get(name=name)
-
-    @staticmethod
-    def SUBVENTION_COF():
-        subvention_cof = cache.get('SUBVENTION_COF')
-        if subvention_cof:
-            return subvention_cof
-        try:
-            subvention_cof = Settings.setting_inst("SUBVENTION_COF").value_decimal
-        except Settings.DoesNotExist:
-            subvention_cof = 0
-        cache.set('SUBVENTION_COF', subvention_cof)
-        return subvention_cof
-
-    @staticmethod
-    def ADDCOST_AMOUNT():
-        try:
-            return Settings.setting_inst("ADDCOST_AMOUNT").value_decimal
-        except Settings.DoesNotExist:
-            return 0
-
-    @staticmethod
-    def ADDCOST_FOR():
-        try:
-            return Settings.setting_inst("ADDCOST_FOR").value_account
-        except Settings.DoesNotExist:
-            return None;
-
-    @staticmethod
-    def OVERDRAFT_DURATION():
-        overdraft_duration = cache.get('OVERDRAFT_DURATION')
-        if overdraft_duration:
-            return overdraft_duration
-        try:
-            overdraft_duration = Settings.setting_inst("OVERDRAFT_DURATION").value_duration
-        except Settings.DoesNotExist:
-            overdraft_duration = timedelta()
-        cache.set('OVERDRAFT_DURATION', overdraft_duration)
-        return overdraft_duration
-
-    @staticmethod
-    def OVERDRAFT_AMOUNT():
-        overdraft_amount = cache.get('OVERDRAFT_AMOUNT')
-        if overdraft_amount:
-            return overdraft_amount
-        try:
-            overdraft_amount = Settings.setting_inst("OVERDRAFT_AMOUNT").value_decimal
-        except Settings.DoesNotExist:
-            overdraft_amount = 0
-        cache.set('OVERDRAFT_AMOUNT', overdraft_amount)
-        return  overdraft_amount
-
-    @staticmethod
-    def CANCEL_DURATION():
-        cancel_duration = cache.get('CANCEL_DURATION')
-        if cancel_duration:
-            return cancel_duration
-        try:
-            cancel_duration = Settings.setting_inst("CANCEL_DURATION").value_duration
-        except Settings.DoesNotExist:
-            cancel_duration = timedelta()
-        cache.set('CANCEL_DURATION', cancel_duration)
-        return cancel_duration
-
-    @staticmethod
-    def create_missing():
-        s, created = Settings.objects.get_or_create(name='SUBVENTION_COF')
-        if created:
-            s.value_decimal = 25
-            s.save()
-        s, created = Settings.objects.get_or_create(name='ADDCOST_AMOUNT')
-        if created:
-            s.value_decimal = 0.5
-            s.save()
-        s, created = Settings.objects.get_or_create(name='ADDCOST_FOR')
-        s, created = Settings.objects.get_or_create(name='OVERDRAFT_DURATION')
-        if created:
-            s.value_duration = timedelta(days=1) # 24h
-            s.save()
-        s, created = Settings.objects.get_or_create(name='OVERDRAFT_AMOUNT')
-        if created:
-            s.value_decimal = 20
-            s.save()
-        s, created = Settings.objects.get_or_create(name='CANCEL_DURATION')
-        if created:
-            s.value_duration = timedelta(minutes=5) # 5min
-            s.save()
-
-    @staticmethod
-    def empty_cache():
-        cache.delete_many([
-            'SUBVENTION_COF', 'OVERDRAFT_DURATION', 'OVERDRAFT_AMOUNT',
-            'CANCEL_DURATION', 'ADDCOST_AMOUNT', 'ADDCOST_FOR',
-        ])
 
 class GenericTeamToken(models.Model):
     token = models.CharField(max_length = 50, unique = True)