This patch implements the list panel system D7490 for FCurve modifiers.
Although reordering of FModifiers was not implemented before, drag and drop is also implemented here.
This also adds support for regions with panel categories to the list panel system, which was a simple oversight.
There are still problems:
- Context doesn't work in NLA editor
- Lots of memory leaks for anim context. Should find a different method for getting the context that doesn't require a "free" every time.
I'm mainly wondering if there is an existing general way to get the FModifier and its owner_id both without allocating an entire bAnimListElem just to get the owner_id, and common between the NLA editor and the graph editor.