[noticket] Fix paster commands that fail due to

    The synchronous_search plugin is enabled automatically in ckan/plugins/core.py so a few paster commands failed trying to load it again.
    Looks like this was broken since 2371c05c 2013-04-05.

    Affected: create-test-data, dataset delete, dataset purge.
[#1038] Fix display of tree hierarchy, broken in reversal af6c039.
[#1038] Setting of parent group in the form is now done via group['groups'] rather than custom 'parent'

Removed explicit creation of Members in the create/update logic functions - these were a hangover. Instead, the form just needs to ensure the parent group gets added to the group['groups'] and it will get set in the model_save as normal.

Group.get_group no longer used anywhere (and the caching looked ropey anyway) now that the previous bit is removed.

Added schema validator to ensure that no loops form in the hierarchy.

Downwards CTE needed ordering as found it also couldn't be relied upon to be in order it recursed, probably due to the join.

Removed duplicate 'groups' key in the group schema.