0031431: Visualization, PrsMgr_PresentableObject - simplify HLR computing interface

0031431: Visualization, PrsMgr_PresentableObject - simplify HLR computing interface

Multiple PrsMgr_PresentableObject::Compute() methods have been replaced by single one
PrsMgr_PresentableObject::computeHLR().
Dummy implementations of previously declared methods have been removed
from AIS classes not implementng HLR presentation.
Class Prs3d_Projector has been removed and Graphic3d_Camera is now passed directly,
so that redundant dependency from HLRAlgo_Projector in Prs3d interfaces has been eliminated.
StdPrs_HLRShape and StdPrs_HLRPolyShape now implement common interface StdPrs_HLRShapeI.