Backporting to API 14-16, bugfixes
-some styles still not working correctly
-untested on real device

AboutActivity:
-fixed bug where updates dialog would not show due to invalid context

AdvancedSettingsActivity:
-moved quicksilence settings here to be with over intervals
-fixed bug where quicksilence dialog would show a minutes value 1 greater than the stored value

MainActivity:
-commented out API 21 code
-fixed bug where calendar icon in error could be drawn twice

SelectCalendarsActivity:
-added error to be shown when no calendar accounts are available
-added button to add account if none are found
-switch and listview now hidden if no calendars are found

SettingsActivity:
-commented out API 21 code
-moved quicksilence settings to AdvancedSettingsActivity

-removed ripple base from action button drawables, will need to be readded to API 21 resources later