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/forms.py

@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 
+from datetime import timedelta
 from decimal import Decimal
+
 from django import forms
 from django.core.exceptions import ValidationError
 from django.core.validators import MinLengthValidator
@@ -8,12 +10,16 @@ from django.contrib.auth.models import User, Group, Permission
 from django.contrib.contenttypes.models import ContentType
 from django.forms import modelformset_factory
 from django.utils import timezone
+
+from djconfig.forms import ConfigForm
+
 from kfet.models import (
     Account, Checkout, Article, OperationGroup, Operation,
-    CheckoutStatement, ArticleCategory, Settings, AccountNegative, Transfer,
+    CheckoutStatement, ArticleCategory, AccountNegative, Transfer,
     TransferGroup, Supplier)
 from gestioncof.models import CofProfile
 
+
 # -----
 # Widgets
 # -----
@@ -379,40 +385,42 @@ class AddcostForm(forms.Form):
             self.cleaned_data['amount'] = 0
         super(AddcostForm, self).clean()
 
+
 # -----
 # Settings forms
 # -----
 
-class SettingsForm(forms.ModelForm):
-    class Meta:
-        model  = Settings
-        fields = ['value_decimal', 'value_account', 'value_duration']
 
-    def clean(self):
-        name = self.instance.name
-        value_decimal = self.cleaned_data.get('value_decimal')
-        value_account = self.cleaned_data.get('value_account')
-        value_duration = self.cleaned_data.get('value_duration')
+class KFetConfigForm(ConfigForm):
 
-        type_decimal = ['SUBVENTION_COF', 'ADDCOST_AMOUNT', 'OVERDRAFT_AMOUNT']
-        type_account = ['ADDCOST_FOR']
-        type_duration = ['OVERDRAFT_DURATION', 'CANCEL_DURATION']
+    kfet_subvention_cof = forms.DecimalField(
+        label='Subvention COF', initial=Decimal('25'),
+        max_digits=6, decimal_places=2,
+    )
+    kfet_addcost_amount = forms.DecimalField(
+        label='Montant de la majoration', initial=Decimal('0'), required=False,
+        max_digits=6, decimal_places=2,
+    )
+    kfet_addcost_for = forms.ModelChoiceField(
+        label='Destinataire de la majoration', initial=None, required=False,
+        help_text='Laissez vide pour désactiver la majoration',
+        queryset=(Account.objects
+                  .select_related('cofprofile', 'cofprofile__user')
+                  .all()),
+    )
+    kfet_overdraft_duration = forms.DurationField(
+        label='Durée du découvert autorisé par défaut',
+        initial=timedelta(days=1),
+    )
+    kfet_overdraft_amount = forms.DecimalField(
+        label='Montant du découvert autorisé par défaut', initial=Decimal('20'),
+        max_digits=6, decimal_places=2,
+    )
+    kfet_cancel_duration = forms.DurationField(
+        label='Durée pour annuler une commande sans mot de passe',
+        initial=timedelta(minutes=5),
+    )
 
-        self.cleaned_data['name'] = name
-        if name in type_decimal:
-            if not value_decimal:
-                raise ValidationError('Renseignez une valeur décimale')
-            self.cleaned_data['value_account'] = None
-            self.cleaned_data['value_duration'] = None
-        elif name in type_account:
-            self.cleaned_data['value_decimal'] = None
-            self.cleaned_data['value_duration'] = None
-        elif name in type_duration:
-            if not value_duration:
-                raise ValidationError('Renseignez une durée')
-            self.cleaned_data['value_decimal'] = None
-            self.cleaned_data['value_account'] = None
-        super(SettingsForm, self).clean()
 
 class FilterHistoryForm(forms.Form):
     checkouts = forms.ModelMultipleChoiceField(queryset = Checkout.objects.all())