Bug 972871 - [Calendar] custom font with vector icons used by visual refresh r=gaye

this patch contains *most* icons needed by calendar visual refresh (maybe all icons)

we will use the custom font during visual refresh development and profile the performance afterwards. (we are aware of perf penalty on app startup - Bug 951593)

![screen shot 2014-04-23 at 20 00 17](https://cloud.githubusercontent.com/assets/155633/2784372/bc1fb6ae-cb3b-11e3-94cd-d63d087f2058.png)

decided to save the icomoon JSON instead of SVG font since it's easier to import and contains extra data.