This takes the existing properties widget in the new material editor and
makes it reusable across multiple applications. It's now added to the
Armoury which shows the gear's used materials. It's also added to the
Data Explorer which now supports viewing material files.
I fixed the render viewport crashing when hiding it again, and made it
even more resilient.
There's no "selection" of possible material properties yet, but shows
keys/values set for the material and falls back to the shader defaults
when needed.
