ArtistDataAdapter

- Updated ArtistDataAdapter with onLoadFinished(), onLoaderRest(), and
onDestroy.
- Changed ArtistDataAdpater to extend Fragment instead of ListFragment.
- Changed PagerAdapter in MainActivity to use just the ArtistDataAdapter
as a Fragment, until the Adapters for the other categories are finished.
- Updated MediaDatabase and DataSources to close the connection at the
proper place.
-Updated android version to 19 (from 17)