Merge pull request #294 from emorency/feature/OPAL-1910-Taxonomies-UI

OPAL-1910: General Config UI and Taxonomies
OPAL-1973 Derived variables can only be removed or edited by the view resource
OPAL-1973 Remove variable implemented in Variable presenter
Test fix
Allow to remove a group with users but show a more specific confirmation message in this case: "Please confirm that you want to remove the group '{0}'. The group '{0}' will be removed for users belonging to this group."
Merge pull request #295 from emorency/feature/User-Groups-Validation

Allow to remove a group with users but show a more specific confirmation...
OPAL-2032 Update variable list, with filter if any
Test save taxonomy
Support update for orientdb document
Test UserService
Test OpalGeneralConfigService
Fix compilations issues due to User refactoring
Rename
Move DefaultDatabaseRegistry to service.impl package
Move Test Spring config as inner class
Fix null lastUpdate timestamps
Fix userService call
Rename test configs
remove empty test
Remove unused field