Merge pull request #109 from graspapp/improvements

Teachers are able to delete units. Closes #107
Add P and G levels. Closes #111.
Merge pull request #112 from graspapp/g-and-p-levels

Implement P and G levels.
Allow teachers to edit units. Closes #108.
Merge branch 'master' of github.com:graspapp/grasp into improvements

Conflicts:
	app/views/units/show.html.erb
Remove mysterious extra delete unit button.
Password recovery
Fixed delete unit. Removed silly mistake in password recovery.