Implement SwipeRefreshLayout

Forced sync is now possible by swiping down like e. g. in the G+ or
GMail-App.
Only enable swipe refresh for own list
Don't try to sync if there is no connection
Use synctask() for forced sync

forcesync() has done the same, so it was implemented twice (thx @ratan12
for pointing at it).
Fix notifications for synctask()

Only disable notification for swipe refresh.
Don't use holo colors from android resources

They are available for API 14+ only
Show loading indicator if forced update and clear=true
Merge pull request #180 from d-sko/swipe_refresh

Implement SwipeRefreshLayout