Feature : Tiled preview initial commiy
Merge branch 'master' into feature-tiled-preview
TiledPreview : follow up
Tiled preview : mutualize canvas background update

When user changes canvas background, css class now applied on document
body.

Created new controller listening to Events.USER_SETTINGS_CHANGED to handle
this.
Fix : set name for tiled background checkbox
Merge branch 'master' into feature-tiled-preview
Merge
Merge pull request #180 from juliandescottes/feature-tiled-preview

Feature tiled preview