Obj3Ctrl description

This class overrides a number of things ObjectControlClass found in ObjCtrl.h and add
some extra functionality to deal with 3 dimensions instead of 2, plus Block and Layer
filtering.

Instances of 3D Object Controls types exist in their appropriate modules (eg. Vertex.cpp)
but an array ControlClasses[] provides objective access for Edit3D.cpp menus.
To add a new type, ControlClasses[] = {}, OBJECT_TYPES and enum CONTROL_TYPES needs to
be augmented.

bool Match(ObjectClass*,BlockClass*,LayerClass*)
  Objects passed are checked using their appropriate ControlClass to see if they match
  the given block and layer.
  
bool Match(ObjectClass*, BlockClass*)
  Same as Match except allows all layers.
  Used in the primary recursive Draw() function in FindVisu.cpp

bool GetLimits(ObjectClass*,int&,int&,int&,int&,int&,int&)
  3D version of the 2d GetLimits function. Used to get an idea of where the object
  would appear on the screen (if at all) and it's current visibility.


