Added testcases based on Mockito.
Fixed JavaDoc.
Use mockito in all test cases.
Added exception test when primary key element does not exist.
Added new method that shows how to search with regular expressions.
Added some new method stubs that should be implemented by the teams.
Added new method to change user data.
Added deletion of users.
Added new method to search for all locked users.
Removed example test classes.
Activated Checkstyle.
Fixed argument ordering in constructor.
Merge branch 'master' into fix-argument-order