First part of major refactoring and Swift porting

- Refactored away almost all table cell subclasses
- Created SUSURLConnection for doing asynchronous NSURLConnections to the Subsonic server using blocks for callbacks
- Fixed player button not showing in CustomUITableViewControllers
- Ported CustomUITableView(Cell), other cells, and CellOverlay to Swift
- Ported CustomUIAlertView to Swift
- Ported FoldersViewController to Swift
- Ported ModalAlbumArtViewController to Swift
- Ported StoreViewController to Swift