Anton/sync groups and verticals

This fixes https://openedx.atlassian.net/browse/BLD-1095

NB: before merge `ENABLE_GROUP_CONFIGURATIONS` should be set to default value.

Please review: @tymofij  @cahrens 

@explorerleslie Sandbox is http://studio.auraz.m.sandbox.edx.org/
yes, tests in parent class test this code:
```
        for hidden in self.HIDDEN_CONTENT[user_tag]:
            self.assertNotIn(hidden, content)
```
see https://github.com/edx/edx-platform/pull/4777/files#diff-203d3213352b9dd8c69094afabe5b066L128