All feature settings are replaced by the received object so the use of
PATCH does not make sense here. The session is "patched" but the HTTP
verb always relates to the URL which refers explicitly to features in
this case.

See https://tools.ietf.org/html/rfc5789.

This upgrades Spring Framework to version 4.2.

See http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#new-in-4.2.

This disables CORS for this path. It should not be usable by external
websites.

This prevents DoS attacks caused by request loops.

Renamed optional.arsnova to ui.arsnova-slogan and made comments start
with an uppercase letter.

WE Offshore Sprint: Session Info Feature

We had the task to implement a Session-Info Form, where the speaker
could add more information to a session, which is already created or to
add more information to a session which is created at that moment.

Therefore we needed to use the update Method and change some code in the
backend as well:

1. Changed **updateSession** Method in SessionService
  * First: we get the session that should be updated from the DB with
    the getSessionFromKeyword-Method
  * Second: we update the values of the session with the new values that
    were entered
  * Third: we check the logo just like in the saving Method of a session
  * we return the updated session
2. Changed **getSessionFromKeyword** Method in CouchDBDao
  * We added these fields, so that they are also fetched:
     * ppAuthorName
     * ppAuthorMail
     * ppUniversity
     * ppLogo
     * ppSubject
     * ppLicense
     * ppDescription
     * ppFaculty
     * ppLevel

See merge request !7

refactored handling of logo during the saving of a new session and the update of an existing session out into a new method handleLogo

Retrieved @Cacheable and changed updateSession method in SessionService, now getting the session by keyword and set all fields that may have changed to a new value