fill graphs on profile page

- caffeine.models:
  - add hour_result_dict, month_result_dict, year_result_dict,
    weekdaily_result_dict to prepare result dictionaries
  - add docstrings
  - add statistic query methods to CaffeineManager: hourly_caffeine_for_user,
    daily_caffeine_for_user, monthly_caffeine_for_user,
    hourly_caffeine_for_user_overall, weekdaily_caffeine_for_user_overall
- caffeine.views:
  - add statistic query results to ProfileView.get_context_data
- coffeestats.settings.base:
  - redefine TIME_ZONE
- caffeine/static/caffeine/js/validation.js:
  - add sanitize_datetime and prerequisites
- templates/includes/js_charting.html:
  - add functions drawBarChart and drawLineChart
- templates/profile.html:
  - add form validation for coffee and mate forms
  - add JavaScript code to render the charts