Started adding pretty-printers for the various types in the music model.
Merge branch 'music_dev' of https://github.com/GL-MPRI-2014/GL_MPRI_2014 into music_dev
Started adding pretty-printing facilities for all defined structures.

For debugging purposes.
First iteration of settings screen
Completed print_pitchClass implementation
Added back button
Quick visual refactoring on function print_pitchClass.
More logical position
Added settings object
Updated settings (+ fix doc)
Use of settings in Camera
Changed the way Home.screen works (step 1)
Draft for new Home.screen and items

The idea is to generalize the items used and drawn
in the main and setting screens.
I want them to be more generic and eventually (don't worry
@Vlanvin) to merge them them with BaseMixins.
I will later implement classes for easy setting manipulation.
We want modal < actionnable < item
First implementation of future item and actionnable
Merge branch 'master' into settings

Conflicts:
	src/interface/Camera.ml
Continued work on pretty_printing
New interface for home screen
Added modal item
has_focus is now protected (and in the mli)