Merge pull request #449 from solispauwels/master

Documentation update
Added .gitkeep to files that don't have to be remove of the file system in raw_install process
Merge branch 'master' of https://github.com/claroline/Claroline
Merge pull request #450 from maxailloud/master

Added .gitkeep to files that don't have to be remove of the file system in raw_install process