Changed voting dialog to only display one tab per answer.

No tests for this, yet.

Conflicts:
	common/lib/xmodule/xmodule/crowdsource_hinter.py
	common/templates/hinter_display.html
Fixed tests to work with new vote-tabbing method.  Fixed some string-int incompatibility errors.

Conflicts:
	common/lib/xmodule/xmodule/crowdsource_hinter.py
	common/lib/xmodule/xmodule/tests/test_crowdsource_hinter.py
Refactored formula response grader to expose formula-evaluating to outside world.

In preparation for adding hints to formula response.
Hinter now works with formula responses.  Tests broken.
Crowdsourced hinter now supports formula responses.  Tests still broken.
Fixed numerous 500 errors that result from mal-formatted post requests.

Fixed tests to work with symbolic answer changes.
Changed hint voting ui to show all hints on one page.

Fixed broken tests for hint manager.