Blender Git Loki

Support multiple panels of the same type

The name for the uiBlock associated with a panel was just the panel type's
idname, so the old block found at the start of drawing was the same for
every panel of a certain type.

Panel blocks for list panels are now named with the list index appended
to the end of the name. The panel list is also rebuilt when reordering
panels of the same type.