Upgrade to Django 1.8

[merenbach]

Django 1.8 is a long-term support release:

Additionally, the Django team will occasionally designate certain releases to be “Long-term support” (LTS) releases. LTS releases will get security and data loss fixes applied for a guaranteed period of time, typically 3+ years, regardless of the pace of releases afterwards.

Some changes include how the Django template system is configured in settings.py. Since development environments will ideally work with the same settings.py as production, a general path could be:

1. Create a new app in Django 1.8. Customize default directory names as desired.
2. Merge in "global" settings to settings.py. These apply regardless of whether the program is running in development, production, etc.
3. Set up settings.py to read environmental vars from a .env file, which can be in place on production and staging servers as well as local boxes. This would contain things like secret keys, mail server credentials, etc. A default file under source control (say sample.env) should be "copyable" to .env with little to no tweaking to get a local install up and running.
4. Update settings.py with new settings names and formats. Template configuration has been refactored, for instance.
5. Update source to fix deprecated code.
6. Perform whatever testing is required prior to being production ready.

[bestan]

After the upgrade is completed, it's worth replacing django-aggregate-if dependency introduced in https://github.com/bestan/mchp-dev/commit/37e0eff9c84fefaafc29a6843143b6be5c519edb with https://docs.djangoproject.com/en/1.8/ref/models/conditional-expressions/#conditional-aggregation