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 
Python unit tests are run on Jenkins. But we have not solved issue with bok_choy on Jekins for now, and that is why we do this way.