Wholescale changes to how some of the parsing parts work.

Working on making the differences between the different models clearer.

Unlabelled / Labelled / Undirected

MST:      60.7 / 54.5 / 78.3
MST+v:    62.6 / 56.9 / 79.3
MST+v+qg: 62.7 / 56.6 / 79.6