Fix for editor button
Fixed an issue where on closing the flow manager the code that hides/shows the ContentTools editor button wasn't syncing the regions the editor can see and therefore didn't cope with scenarios where all snippets were removed or a snippet was added to an empty flow.
In addition I've changed some of the base API URLs:
snippet-scope
becomeschange-snippet-scope
snippet-settings
becomesupdate-snippet-settings
This change would break previous versions (though it's easy to override by creating your own API), it was made to provide better clarity of the roles of those endpoints.