create BookmarkManager
create local database, implement database setter
load bookmarks from database if up to date
independent of time synch, partial fix for deletion detection
prevent reopening of database connection
fallback for old semantic scuttle API
refresh bookmarks on settings change
Merge branch 'local-storage' into testing

Conflicts:
	src/gr/ndre/scuttloid/BookmarkAddActivity.java
	src/gr/ndre/scuttloid/BookmarkEditActivity.java
	src/gr/ndre/scuttloid/BookmarkManager.java
	src/gr/ndre/scuttloid/ScuttleAPI.java
	src/gr/ndre/scuttloid/database/DatabaseConnection.java
	src/gr/ndre/scuttloid/database/DatabaseHelper.java