Matthieu/gm based fs image

hey Jed, 

I just finished to update the whole system, using node module gm, but not including it within keystone dependencies. I also updated the fsimage UI, and changed the way we can access pictures template side ( everything is explained in the FsImage.js field file, a big example at the beginning ). I also commented most of the code and removed most of the useless code parts :)

I think there's actually few things to discuss, cause I opened some new directions and I'm not sure which one choosing, or which one you prefer. So, I'm looking forward hearing from you :)

I also had few problems avoiding the include of gm within keystone dependencies, had to hardlink it with npm link to be able to test. I Don't know what's the best solution for that...