MotD Feature:

There are two types of MotD: 
AdminMessages
SessionMessages

Every Message has a title, text, start- and enddate.

You can declare an admin account in the arsnova.properties (security.adminaccount = <adminusername>) and with this account you can create Messages for different audiences (different types are: all (shown on startpage), loggedIn, students, tutors) which will be shown in a messageBox.

SessionMessages can be created for every session by the sessioncreator and is displayed, when you enter the session.

When a user that is not logged in via Guest, he pushes a list to the backend with all the messagekeys he read and acknowledged, so that he isn't shown the same messages over and over again. In addition to that, the keys are also stored in the localStorage (e.g. for guest accounts).

See merge request !15

Diabled Checkstyle's Checker.TreeWalker.RedundantThrows module which no
longer works with plugin version >=2.16.

 - add controller/service/entity/dao-functions
 - add motdlist so that users can tell the backend, which motds they have read
 - add admin account (in arsnova.properties: security.adminaccount).
 - add permission function for admin

Version information is now compiled as part of a build and written to
version.properties. It is exposed by the API.

Markdown and learning progress features are no longer considered
experimental. Leaning progress can no longer be globally disabled.

Added 'ui' prefix for splash screen settings.

Upgrade to Spring IO 2.0.1.RELEASE

Add "liveClicker" use-case and possibility to lock live feedback

### Live Clicker
An additional use-case called "liveClicker" has been added (https://scm.thm.de/redmine/issues/17162). It uses the live feedback implementation in order to make the voting in the style of hardware clicker  systems possible. The timed deletion of feedback votes has been disabled for sessions with "liveClicker" configuration.

### Feedback lock
The feedback-lock feature allows the speaker to lock the live feedback/clicker. While the lock is active, no further votes are possible. On lock removal all votes from the session will be reseted.



See merge request !13

Feedback reset will be disabled for liveClicker-sessions.

Add support for LDAP manager and search

New configuration settings have been implemented to allow additional
LDAP environments:
* `security.ldap.user-search-filter`
* `security.ldap.user-search-base`
* `security.ldap.manager-user-dn`
* `security.ldap.manager-password`

See merge request !12

An LDAP search pattern can now be used instead of binding with a DN
pattern.

This reverts commit fc78eb18.

SASS variables only exist at compile time and are not available for
arsnova.properties.

Paul-Christian Volkmer authored 9 years ago and Daniel Gerhardt committed 9 years ago

See http://platform.spring.io/platform/ for more information about it.

This patch makes Spring.IO usable with ARSnova Backend and also updates
some dependiencies not beeing upgraded in ARSnova Backend POM
so I removed explicit version declaration.

Problems with json-path-assert dit not occure, so i removed version
declaration and use managed version 2.0.0.

Remove obsolete version properties

Closes GH-17. This is a squshed version of PCV's PR. (DG)

Swagger api

new descriptions for the swagger api doc in the entity-classes

See merge request !11

Add a default exception handler to catch non handled exceptions

The default exception handles all excaptions not handled by the
following handle methods.

It creates a response, containing the HTTP status description
and the exception message.
This response can be serialized into JSON.