Make the LSJON importing ordered
Make the LJSON import use PointGraph

Create a pointgraph if there is valid connectivity
information
Reorder the labels

Keep the order stable so that PTS to LJSON and back works
properly. The order MUST be maintained to make sure that the
underlying pointcloud maps back and forth
Update landmark.py
Update landmark.py
Merge pull request #439 from patricksnape/labelling_fixes

Labelling fixes
Merge pull request #440 from jabooth/iop

pathlib.Path can no be used in menpo.io
Merge pull request #441 from jabooth/booleanconstrain

adds constrain_to_landmarks on BooleanImage
Merge remote-tracking branch 'upstream/master' into correspond