23250: [CEA 1766] 3D tab is empty when editing mesh

23250: [CEA 1766] 3D tab is empty when editing mesh

+ minor changes in docs

+ fix other problems with Mesh Dialog:
1) at mesh edition, old hypothesis remain assigned after playing with
   Mesh Type and Hypo Sets (change is in isSelectedHyp())
2) When a 3D algo is unset due to change of Mesh Type, its hypotheses remain
   assigned and a new hyp can be created