Single-user mode GUI

 - Shows a dialog allowing to choose between tags or tracks seed types when creating a new playlist
 - Shows a multi-selectable dialog for the available tags (hard-coded in res/arrays.xml)
 - Had to make some little changes due to the usage of support library (requested in order to use classes such as
   DialogFragment or methods such getActivity())
Single-user mode GUI

 - Const.java: improves SeedType ENUM
 - SoloPlaylistsActivity.java: improves seed types and seeds handling through dialogs
Single-user mode

 - Introduces the Playlist object (empty nutshell for now)
Fix NullPointerException
LibraryService NullPointerException prevention

Improves cursor closing
Single-user mode

 Partial commit, before going back home.
 Identified the exception when trying to send tags to the server: JSONObject is not the right type to be passed to
 the API as a param.
Refactoring

 - Creates a new "ch.epfl.unison.data" package specific for dealing with android sqlite database
 - Deprecates LibraryHelper (UnisonDB to be used instead)

Other stuff
 - Fix ClassCastException when sending the seeds for a new playlist by changing the request from GET to POST
Single-user mode

 - defines tables for handling tags in sqlite db
Single-user mode

 - Implements methods to handle Tags on sqlite db
 - Uses these tags
Removes moved file from original place
Updates tags handling

- The whole process to fetch the top tags from the gs server is updated.
- Corresponding data structures are updated as well
Single-user mode

- Makes use of Playlist object
- Introduces context menu for playlists list
- Uses generic layout list.xml
Single-user mode

- Updates database:
  - table "tags" renames to "tag"
  - adds "is_checked" field
- Updates according to changes above
Changes tag seeds selection handling

- introduces is_checked field in tag table

Misc:
- FIX not autoincrementing row id in lib_entry table
Updates tags selection

Tags are now correctly sent to the server!
JsonStruct and UnisonDB: Updates labelling of fields
Merge branch 'groupSuggestion' into master

Conflicts:
	res/menu/menu.xml
	src/ch/epfl/unison/api/UnisonAPI.java