#528022 by tha_sun: Change wording of "Add variant" to "Create variant" to avoid confusion with the "Add variant" tab.

basics are in place.

Add validation against the alias table to prevent users from creating paths that are already aliased.

Add enable/disable capability to node, user and term views. Make them disabled by default. Improve descriptions of these items.

Visible enabled/disabled markings on list; allow direct enable/disable from list, plus sorting and filtering on enabled/disabled status.

Fix "add variant" workflow which had broken when the link moved from the handlers menu to the actions menu.