Added new service for comments.

* Moved classes from `de.thm.arsnova` root package.
* New util package
* Do not start interface names with `I`. Appended `Impl` to the
  implementing class instead.
* Renamed learning progress classes to score and move them from
  `.domain` to a new `.services.score` package.
* Do not capitalize acronyms in class names:
    * CASLogoutSuccessHandler -> CasLogoutSuccessHandler
    * SocketIO* -> Socketio*
* Renamed `.socket` package to `.websocket`

(Lecturer/Skill)Question has been renamed to Content. Method names have
not been touched yet to ease reviewing the changes.

Additionally, remove unused loggers.

remove spingfox for ApiIgnore direction
use swagger-maven-plugin to generate swagger.json before compiling rather than
 dynamically generate it on request

Updated copyright year and adjusted header format to be consistent over
all files and with other ARSnova projects.

/questionbylecturer/* => [/session/{sessionKey}]/lecturerquestion/*
/questionbyaudience/* => [/session/{sessionKey}]/audiencequestion/*

API changes:
- /session/visitedsessions => /session/?filter=visited
- /session/mysessions => /session/?filter=owned
Added changed routes to LegacyController.

Removed sessionKey from routes if it is not needed.
Changed sessionKey from PathVariable to RequestParam if still needed.
/session/{sessionKey}/question/* => /question/byaudience/*
Added redirections for legacy routes to LegacyController.

LegacyController.