Added icon to navbar header.
Added a "timezone" column to the User model.

It will store the timezone selected by the user. Times in the views will be localized to this timezone; specifically, the publish datetime of entries.
Users can select their timezone when signing up.
Users can change their timezone from the Edit Registration view.
Publish time of entries is displayed in the timezone selected by the user.

This doesn't apply to entries from previous years, for which the time is not displayed.

Previously all publish times were UTC, which could confuse the user in some cases. Now publish times are displayed in the user's local time (as long as he's correctly set his timezone).