Allow hemimandibulectomies

[mauigna06]

As this comment asks:

Tumour at the left mandible requires hemimandibulectomy including left condyle. However, BRP needs 2 saw boxes (1st and last cutting planes) in order to proceed next step. Basically, intraoperatively only need one osteotomy site (in this case located at the left body of mandible). Noted orange arrow indicates part of mandibular base. It is a must and should be touching the cutting box for boolean operations to be performed.

[mauigna06]

This should be set with a label that says "after resection" and a combobox with options: keep both sides, keep left side only, keep right side only

[mauigna06]

Almost finished, only needs documentation

[mauigna06]

There is a bug when creating the neomandible 3D model for hemimandibulectomy mode. It's because there is no contact between resected mandible left and the bone segment of the contra-lateral side. The issue may be solved using the new boolean operations logic