First draft of converting ListViews from SoloMainActivity to fragments

* Renames ids in layouts
* If the ListView is empty, an "emptiness" message is shown
* Some refactorization due to better understanding of how the fragments work
  and communicate.
Comments all stuff related to old SoloPlaylistsActivity layout
Fetches the number of tracks contained in a playlist
Works in progress with fragments
Goes on with f**king fragments
Adds Groups and Solo in menu
Adds forgotten GroupsActivity start in AbstractMenu
Hides menus if useless (solo in solo, groups in groups)

The Solo menu entry is hidden in the solo activities. The same rule stands for
the groups activities.
FIX missing group stats

Many fuzzy stuff about Fragments.
I think I hadn't seen much in the lists because of a not so stable android
layout template from dev.android.com.
I'll start again from null tomorrow, and will work hard to make these fragments
display some content. Hope it'll go fine...
Remote playlists fragment displays the remote playlists :D

This doesn't sound really exciting, but for me it's a great achievement ;)
It's not about displaying playlists, it's about understanding these fragments
and getting them displaying the content I want the way I want.
Merge branch 'dev/solo'

Conflicts:
	AndroidManifest.xml
	res/values/strings.xml
	src/ch/epfl/unison/ui/GroupsMainActivity.java
	src/ch/epfl/unison/ui/SoloPlaylistsActivity.java
	src/ch/epfl/unison/ui/SoloTracksFragment.java
Removes deprecated and commented code, updates Fragments referencing and access
Adds "Create" menu item in solo mode

FIX trying to hide groups menu in GroupsHistory (no menu at all)
Ends up ListViews conversion to Fragments (beta tests are successfull)

Each the local and the remote playlists lists are functionnal. Creating a new
playlist, saving it to the device, remove it from device are working quiet well.
Removing form the remote list is buggy, to be fixed soon.

A "+" button is added in the action bar to allow creating new playlists.

Else, the code of the SoloPlaylists* is cleaned, a lot of commented code is
removed.
FIX optionMenu and contextMenus in solo mode

Restores the click handling on option menu items, prevented during a previous
refactoring.
Refactorizes the solo playlists context menus to one single xml file.
FIX wrong onContextItemSelected call from a fragment.
Refactorizes ArrayAdapters and list row layouts

PlaylistsAdapter and TracksAdapter are now subclasses of Uutils
(PlaylistsAdapter is shared between at least two classes), making these
adapters usable for any activity of the project.

With the idea to make it a little more explicit, every layout describing a row
of a list is prefixed by "listrow", such that every such listrow layouts are
naturally grouped by name.
The row list layouts outside the scope of the solo mode are kept for
compatibility reasons, but they're intended to be removed after the merge with
the other branches.

Deprecated layouts such as list_fragment and solo_playlists are removed, since
they're no more used.
Organizes imports
Formats the project
Highlights the currently played track, by displaying a play icon next to it

Not tested, to be done soon.
Refactorizes SoloMainActivity and its fragments

* Removes unused onPlaylistInfoListener
* Changes visibility of AbstractPlayer.next() from private to default
* Overrides AbstractPlayer.next() in SoloPlayerFragment
* Highlighting the currently played track in SoloTracksFragment doesn't work
* Improves listrow_track: adds an image to the left of the row, to be used to
  highlight the played track

The getListView() count in SoloTracksFragment always returns 0, thus I can't
access the ListView children. I haven't figured out how to overcome this issue
for now, that's why the highlighting doesn't work.

BUG the played track in GroupsPlayer doesn't correspond to the displayed data.
This is probably due to an issue when fetching the track from the DB (wrong
id).