A couple of styles and tweaks.
Tweaks
Merge conflicts
Spreadsheets stuff
Some student-facing and TA-facing views
Groups, graders, summaries
Formatting and better hide/show for spreadsheets grades view.
Merge branch 's3-assignments' of https://github.com/arkon/Markus into s3-assignments

Conflicts:
	app/views/assignments/grader_index.html.erb
	app/views/assignments/student_interface.html.erb