0024961: MeshVS: revision of DRAW commands

0024961: MeshVS: revision of DRAW commands

meshfromstl - display MeshVS_Mesh object in a way consistent with vdisplay command
meshdel - deleted, vremove to be used instead
meshshowall - set empty maps of hidden IDs instead of null handles
meshhidesel - initialize the maps of hidden IDs to avoid exception
meshmat - add optional transparency argument and enable transparency in the viewer if not yet done
meshvectors - command for testing VectorPrsBuilder added

MeshVS: DRAW commands improving
Updating test cases due to previous changes
Small bug in MeshVS_ElementalColorPrsBuilder fixed
vselmode fix
Small correction of test cases for issue CR24961