Add time zone support

[kaputtnik]

Currently we use Django setting USE_TZ = False because of historical reasons. Changing this setting to True means any Datetime field in the Database becomes additional values to store the TimeZone and possible DST. But changing the setting has several consequences: Adjustments to the code, mysql and the database are needed.

Here are some links which could help migrating to activate Time zone support:

- Django Time Zones (general): https://docs.djangoproject.com/en/1.8/topics/i18n/timezones/

- Django migration guide: https://docs.djangoproject.com/en/1.8/topics/i18n/timezones/#migration-guide

- Additional changes to mysql: https://docs.djangoproject.com/en/1.8/ref/databases/#mysql-time-zone-definitions

- Dumpdata could may be helpful to get a json formatted output of database and tables: https://docs.djangoproject.com/en/1.8/ref/django-admin/#dumpdata-app-label-app-label-app-label-model

- Loaddata can be used to load modified json files (fixtures) created by dumpdata: https://docs.djangoproject.com/en/1.8/ref/django-admin/#loaddata-fixture-fixture

[GunChleoc (gunchleoc)]

Issue moved to https://github.com/widelands/widelands-website/issues/271