Blender Git Loki

Disabled reading Groups from bf-blender. There was old rudimentary code
for Groups in official release still, which will give very bad results when
loading an Orange branch file with bf-blender, save over, and read back
in Orange branch.

Now, reading files with Groups in bf-blender will just completely ignore
them (not read nor save). That's destructive, but normal behaviour and
stable.