[Fixed] group messages creation & deletion on C3 FS
[Fixed] GroupList snippet Unit test
[Changed] small cleanup & refactoring of Group Service related code
[Fixed] proper handling of exceptional situations when creating & deleting groups (with appropriate c3 fs mappings)
Merge pull request #22 from ifunsoftware/group-service-cleanup

Various fixes for groups creation&deletion + group messages + refactorings