Fixes + mat sys improvements

Use a loop over all available slots

kinda functional, still needs restructure so that connect_vertex_colors_to_pass and connect_to_output work

not yet functional, but getting there, needs restructure

Switch over to the scene version from the UI panel. Remove version from export operator. Note that the game version should be set manually, as it is not guaranteed to be set correctly on import when games share the same version.

Fixes issues in the root object logic

Pull fixes

Refactor/blender 2.8 ui registration

Merge/bug fix collision bhk mopp list processing

Merge/version string