Import in `ready` method of kfet app config of `kfet.forms` may be
annoying because it starts executing `__init__` methods of fields.
Causing failures if these methods does DB calls, as `ready` may be
called before applying migrations.
- kfet_config gives "reduction_cof" as editable instead of
"subvention_cof"
- this last one can still be accessed via kfet_config (computed from
new "reduction_cof"
- add units to numeric values of kfet_config form
- KFetConfig `set` method now takes model instance instead of their pk
for this type of entries.
- Add tests for KFetConfig class: tests against types currently used by
kfet app (duration, modelinstance, decimal).
- These tests are located in `kfet/tests/test_config.py`. We should
separate tests suites by file like this, considering what they are about.
- KFetConfig method `set_many` renamed to `set` (because it also updates
only one).
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
