implement caffeine submission

- caffeine.forms:
  - add SubmitCaffeineForm to submit new caffeine entries
- caffeine.views:
  - implement SubmitCaffeineView as proper FormView
- coffeestats.settings.base:
  - set USE_TZ to False because all our charts rely on local timestamps and
    USE_TZ leads to UTC timestamps in the database
- templates/profile.html:
  - add {% spaceless %} around forms
  - use proper form id for mate form
  - add default filter to coffee vs. mate values