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.

First phase reviews: @tymofij  @olmar 
Don't persist this change. Just set `active_child.display_name`, and the call `active_child.render(...)`. The point is that when rendering this vertical in the split test, you're just overriding the name for display.