4 OE/ORA UI fixes to make it easier to use
- require confirmation when clicking Open Ended reset button (now working)
- require confirmation when submitting Open Ended essay (now working)
- disable text feedback area during calibration and let users know that they should give feedback when grading
- fixed error message typos
Merge pull request #980 from edx/giulio/ORA-fixes

A few OE UI fixes