1. change save to submit in feedback submit pages
2. fix related tests
Merge remote-tracking branch 'origin/master' into Issue2232

Conflicts:
	src/test/java/teammates/test/cases/logic/CoursesLogicTest.java
Merge pull request #2245 from TEAMMATES/Issue2232

studentFeedbackSubmission: rename button 'save' --> 'submit' #2232