Configuration for Socket.IO has been refactored to support proxies and
replace ambiguous property names:
* Added API property `socketioPath` to `/configuration/`
* Added property `socketio.proxy-path`
* Removed property `security.ssl`
* Renamed properties:
  * `socketio.ip` -> `socketio.bind-address`
  * `security.keystore` -> `socketio.ssl.jks-file`
  * `security.storepass` -> `socketio.ssl.jks-password`

The default port to bind to has been changed from 10443 to 8090 since
SSL is not enabled by default. There is enough room (8081-8089) for
additional severs (e.g. `grunt run`) in development environments.

The security.*.enabled properties are now loaded as booleans.

The original implementation did not correcly implement the W3C
Recommendation (https://www.w3.org/TR/2014/REC-cors-20140116/). CORS is
now implemented based the CorsFilter provided by Spring MVC.

Origins allowed for CORS can now be set in the configuration.
Additionally, GET access to the following request URLs is allowed from
all origins:

* /
* /arsnova-config and /configuration/
* /statistics

The implementation (introduced by
2084f33a) was to permissive and posed a
security risk. As a consequence, cross origin requests requiring client
authentication are no longer possible.

Daniel Gerhardt authored 8 years ago and Tom Käsler committed 8 years ago

There is no need for a separate property. `questionValue` is used by
learning progress views.

Convert database user IDs to lowercase on account creation an login.
Additionally, LDAP UIDs are lowercased as a fallback when they cannot be
retrieved from the server.

Fixes failing start up because of no longer existent
`security.guest.lecturer.enabled` setting.

(https://github.com/thm-projects/arsnova-backend/wiki/Caching
^-- see List of cache entries and associated keys)

In some cases the Socket.IO servers used in test cases are not closed
when starting a new test. In this cases the tests will fail with
an address conflict because an other Socket.IO server is still running.

Using a new port, starting with previous defined port 1234 up to 1243 will
assign every new created Socket.IO server an other address/port.

An address conflict will still occure if an other service is running on
ports from 1234 to 1243, so it is generally a bad idea to have tests in the
hope that no side effects will occure from outside of application scope.

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

fix bug where abstention questions are not exported

fix bug where not all attributes from grid questions are exported

implement: via two booleans you can now decide whether AnswerStatistics and FeedbackQuestions shall be exported, too