Fix user messages

I fixed the local storage service, user messages were jsut working fine.
I updated the UXD, they are now sticky to the right-bottom corner.
Adding overflow markers for preview frame scroller
New scroll overflow design (smaller teeths)
Fix scroller overflows apparitions
Fix background visual design
Update scroller overflows VD + fix zindex bug
Merge pull request #106 from juliandescottes/fix-user-messages

UI Stuff again
Add canvas background switcher

A quick integration to make our minds on different backgrounds and ask
for feedback
Code cleanup + unsued images removal
Add 'visit gallery' action
Fix contextmenu right click (active only above drawing canvas)
Merge pull request #107 from juliandescottes/ui-updates

Ui updates
radial gradient background on FX
Merge pull request #108 from captainbrosset/master

i can haz cross-browser css3 gradient
correct slider init value and better FX slider event handling
Added back the -webkit prefix for radial-gradient used on body
Merge branch 'slider-init' of https://github.com/captainbrosset/piskel into captainbrosset-slider-init
Reverted back to onchange due to lack of support of input range in firefox 21
Merge branch 'master' into gh-pages