Native font instead of images for mobile icons

Edit: DO NOT MERGE, needs tuning for IE + Firefox !!!"!!

This PR makes it extremly easy to use fontAwesome as Icons for the menu.
It's currently only for lower screen resolution instead of the text but we could easily add an ['data-icon'] css outside the media queries in order to get icons to the menu buttons.

This is what it basically changes:

- added fontAwesome fonts and related CSS
- made the menu using the data-icon html5 attribute. …
- added an inidicator class as an alternative to indicate PMs, Mentions etc.
- replaced mobile images with plain fonts, looks much better than images and with using the data-icon attribute it should be easy for mods to extend or replace the icon of a button.
 - fixed some bugs related to resizing the screen.

Depending on the resolution all buttons are available.
![menu_new](https://f.cloud.github.com/assets/1027992/1923650/1235f9e8-7e18-11e3-9687-4d5a6477865a.png)