Fix drawer in mobile version

This is an attempt to fix https://github.com/diaspora/diaspora/issues/4801
I hope it will also fix different weird behavior in mobile browsers (Firefox for Android and Firefox OS).
It also removes the black background on badges and add a float right on the profile picture in the menu, as users suggested (don't remember where :p)
Btw, I started to split the css code from mobile.css.scss to different files. I put it in the mobile folder in stylesheets, I hope I'll have time to more refactor the css pretty soon.

Enjoy :)