Fix of checking existence of group when creating new one

- add parentGroupId to checking of group existence
- add test for two same groups with the same name,parentGroup and voId
Merge pull request #250 from stavamichal/create_group_existence_checking_fix

Fix of checking existence of group when creating new one
GUI: support for CESNET's linker form item

 - if form item with div#cesnet_linker_wrapper is found. It's moved in DOM and loading
   script is appended. Also GUI is moved down to reserve space for linker.