This allows expecting those exceptions in test classes.

LegacyController.

Conflicts:
	src/main/java/de/thm/arsnova/controller/QuestionByLecturerController.java

implementation yet!).

Conflicts:
	src/test/java/de/thm/arsnova/dao/StubDatabaseDao.java

This prevents crashes caused by null pointers. Checks are moved to
the service class, and real objects are passed along.

Removed sessionKey from routes if it is not needed.
Changed sessionKey from PathVariable to RequestParam if still needed.
/session/{sessionKey}/question/* => /question/bylecturer/*

QuestionByLecturerController.

class.

Excluded HttpRestApiTest from build process.

Strings. This fixes incorrect content types being set in the response
header.

Read, unread, and total count for interposed/feedback questions
implemented.

returned by some controller methods.

/canteen/foodvote => /canteen/menu/vote (GET)
/canteen/vote => /canteen/menu/vote (POST)
/canteen/foodvotecount => /canteen/menu/vote/count

/socketurl => /socket/url
/authorize => /socket/assign
Changed status code for /socket/assign to 204 (this does not create).