Fixing ability to select particular calendars to sync
-bumped version code to 7
-2.1.0 beta 2 release

MainActivity:
-now uses an image drawable on the left hand side to display the events color

SelectCalendarsActivity:
-many bugfixes
-list of calendars now refreshed properly
-removed ok and cancel buttons, settings are saved immediately, and the background service is restarting during onPause()
-touching header switch has no effect, must touch the box (new bug)
-still uses older 2px wide layout on left to show calendar color, needs to be switched to new imageview sidebar
-changed activity from a dialog to a full screen activity (may be restored later)

SettingsActivity:
-fixed possible bug where context was being assigned before it was valid
-calendar widgets now properly disabled when the service is set as inactive
-calendar widgets now show a proper background when pressed
-removed commented out API 21 code

Columns:
-removed INSTANCE_ID since the _ID already contains this value

DatabaseInterface:
-update() now only inserts events if all calendars should be synced, or if that events calendar has been selected
-now properly removes events if their calendar has been disabled
-fixed bug where event id was not being inserted into the local database in insertEvent()

EventDatabaseOpenHelper:
-fixed bug from typo in onCreate

DefaultPrefs:
-added setting to sync all calendars by default

Prefs:
-setSelectedCalendars() now removes duplicatate calendar ids before saving the list
-setSyncAllCalendars() now removes any previously saved list of calendars to sync (if needed)