First pass at implementing the activity calendar. Can display activities
properly in a 30 day window. Also first pass at activity info page which
currently displays some basic information about the activity. Both are
still very bare bones.

* Added CalendarActivity to display users activities in a 30 day frame
  relative to the current date
* Added ActivityInfoActivity to display information about an activity.
* Added their respective xml UI description files.
Merge branch 'calendar-activity'