Fix issues with fileupload bar and admin sidebar

Related to: https://github.com/globaleaks/GlobaLeaks/issues/52
Update gruntfile to support watching of file changes
Lots of improvements for Admin UI

* Change the appearance of the form editor
* Improve appearance of Mail configuration pages

This fixes:
* https://github.com/globaleaks/GlobaLeaks/issues/27
* https://github.com/globaleaks/GlobaLeaks/issues/51