EMI: Mangle filename when searching for shared material
EMI: Store materials in costume, not in mesh

When multiple meshes in an EMI costume use the same material each will have
its own Grim::Material instance. If a material used by multiple meshes is
changed by a texi chore the instances will become inconsistent.

With this patch materials are managed by the costume, and there will only
be one instance of each reference material.
EMI: Store active texture index for materials
Merge pull request #798 from inguin/emi-materials

EMI: Refactor handling of materials, fix texture animations