from dan grauer (kromar)

With change use_map_color_emission (which is for volumetrics only) to use_map_emit.

also ignore generated face-images (which have no file path).

Changed how mtl_mat names are generated, so that we can still be sure to always have a unique mtl_name for each key (mat_name, tex_name), yet avoiding to add tex name to mat when not needed.

bpy_extras.io_utils.path_reference() expects a real dir as base_src, not the blend file name!

update addons enabled by default to use 'faces -> tessfaces' also grease pencil scatter and quake map export.

from ed gautier (edddy) 

previous order deprecated.

- remove/comment unused variables
- remove unused imports
- fixed some bugs using incorrect variables

export wardiso spec value when used.

from Lawrence D'Oliveiro (ldo)