Merge pull request #1 from Einenlum/master

Adds a way to create the initial root ##METAROOT## by clicking on a button when installing the application for the first time
Modifications of the README file
Merge branch 'master' of http://github.com/quantumm/projetdL

Pull request by Einenlum : add the metaroot by clicking on a button when installing
Modifications of Einenlum's pull request

In TreeController we rather use the slugInTable function of ThematiqueController which seems more precise
Some vocabular modifications
BUG FIXES

Modification of PropositionType in order not to get ##METAROOT## in the list of choices when the user add a proposition. Use of the slug rather than the id.
Slight modification of the README file
Design based on Bootstrap and Ink
Design commit: inline-block used for the roots' blocks

Note: if you want to remove this design just remove the customization.css file
Logos added to each root
Logo and log in button added to the welcome page
Design modified with sketchy icons
First design for the page which permits to add a proposal
Modifications of the design
Design modifications
Slight modifications of the design
Modification of the thematic page design
Design: modification of proposal's view
Design: modification of the Proposal view
Design: Modification of the profile view
FOSUserBundle: overriding design and forms