PIM-1437 : Separate variant groups and groups

Bug fix: [no]
Feature addition: [yes]
Backwards compatibility break: [no]
Unit test passes: [yes]
Behat scenarios passes: [yes|no] #build-217
Checkstyle issues: [no]*
Fixes the following jira:
 - PIM-1437
 - PIM-1456
 - PIM-1457
 - PIM-1458
 - PIM-1459
 - PIM-1466