math4 theme

This includes math4 theme, along with a minor bugfixes and tweaks all around.
Added ability for students to use Past Answers while maintaining current functionality for instructors
Made Classlist editor 2 use tabber.
Made math4 play a little nicer with hardcoded text box lengths
Merge branch 'math4'
Merge branch 'student-past-answers'

Conflicts:
	lib/WeBWorK/ContentGenerator/Instructor/ShowAnswers.pm