`<Icon />` component about cozy-ui

[y-lohse]

This is what I've been using mostly outside of cozy, and I find it generally a lot easier to use. The color changing alone is worth it imo.

[ptbrowne]

#130

[GoOz]

This is a tricky subject. We chose, at some point, the CSS background solution, with embed svg for better performance. But we didn't have all those apps we have now, we didn't have the issues we have now.
Now may be a good time to reconsider the choice we made then. I'm strongly in favor for inline SVGs, as the browser support is good enough and the pros are so much appropriated for big webapps, but not without thinking it properly. A misuse of SVG sprite could cost a lot.

[ptbrowne]

Closing since #130 is merged