Fix session import

See merge request !49

Readd an empty constructor for deserialization with Jackson. It was
accidentally removed a part of a code clean up in commit
685695a6.

Code cleanup

See merge request !48

Additionally, removed unused empty constructor

Additionally, made first use of it in CouchDBDao.

Additionally, remove unused loggers.

Bump Java source and target versions to 1.8

See merge request !47

SessionServiceTest.testShouldDeleteAllSessionData fails when run on
JDK 8.

This will allow us to use type annotations, lambdas, etc. Documentation
already states Java 8+ as a requirement.

Robin Drangmeister authored 8 years ago and Daniel Gerhardt committed 8 years ago

This fixes WebSocket communication for course sessions. (dg)

Refs GH-40.

Changed `security.facebook.enabled-roles` to
`security.facebook.allowed-roles`.

Clean up code

See merge request !46

* Remove unused code
* Optimize imports (group 10+ and static imports)
* Remove redundant variable assignments
* Replace explicit type parameters with <>
* Remove redundant catch blocks
* Use varargs instead of explicit array instantiation
* Weaken visibility of methods and fields
* Simplify conditions
* Do not use StringBuilder for simple concatenations
* Fix code style
* Remove invalid Javadoc

Split up and rewrite  documentation

See merge request !44