Multi mesh materials

[Simarilius-uk]

Multimesh Material JSON Appearance fix
Implemented:

• added the mesh names to the submeshes rather than just the numerical prefix (only on multimesh)
• added the mesh names to the appearances in the material json so that if multimesh import has 2 meshes with the same named appearances both still get imported.

Fixed:

• Materials being available for multimesh output

Still need to do a bit of work on the Blender side to make appearance selection work, as they dont have the same name the app file has for them (but I'm not sure this has worked previously either)

[dragonzkiller]

Not requesting any particular changes, but some suggestions. Seb can weigh in as well.