Documentation update after new inverse mandible reconstruction feature

[mauigna06]

The workflow has not broken, almost surely the instructions still work, instructions must be reviewed to show users how to take advantage of inverse mandible reconstruction

[mauigna06]

The video tutorial and the text tutorial were used with success during January on Slicer's Project Week (so it should be uptodate) but the users were familiar with Slicer already, newbie Slicer users may need more practise/training before being able to use BoneReconstructionPlannner