Finished implementing new editors.

* Fixed crash due to uninitialised mini editor content.
* Sorting now rearranges rather than replaces the existing plugin list
(yay lambda function!).
* During the sorting process, plugin data is stored in the plugin list,
as the graph is now a temporary object confined to the sorting loop.
* Userlist merging, condition eval and validity checks are deferred to
within the sorting loop.