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/
Another concern with calling `update_item` here is that it's going to confuse the publish system. In particular, these edits will be marked every time a studio author views the split module, even if they don't edit it, which means that the edited_on date will be wrong.