expensive properties should really be methods
face_normals from property to method
pseudoinverse, aligned_soource move to properties
av_aligned_error -> mean_alignment_error GPA
Merge pull request #470 from jabooth/methodsproperties

expensive properties should really be methods
Fix from_mask for Trimesh subclasses

Handle masking tcoords and colours for textured/coloured
trimeshes
Merge pull request #473 from patricksnape/from_mask_fixes

Fix from_mask for Trimesh subclasses
Merge remote-tracking branch 'upstream/master' into hdf5abletopickle