OSNG-48 started to implement PUT Groups

Started to implement PUT Groups functionality by refactoring user provisioning and fixing the behaviour EntityListFieldWrapper.
OSNG-48 wrote a test for put
OSNG-49 started to implement PATCH for Groups

started to implement PATCH for Groups, fixed a bug in EntityListFieldWrapper
(String == isn't a good idea in java)
OSNG-49 implement PATCH for Groups