- TEveProjectionManager:

  Added member 'Bool_t fImportEmpty' - this forces the projection manager
  to also import sub-trees without any projectable elements.
  Useful if one expects a completely parallel element structure in
  projected replica.

- TEveSelection:
  Added method 'void RemoveImpliedSelected(TEveElement* el)' needed for
  deregistration of implied-selected elements during their destruction.

- TEveManager:
  - In PreDeleteElement() check if the element is implied selected or
    highlighted and deregister it from there.
  - In function InsertVizDBEntry():
    a) added argument 'Bool_t update';
    b) when replacing the model-element copy its children to the new
       model and optionally update their viz-params.

- TEveElement:
  - Add methods to simplify propagation of visualization-parameters
    between model-elements and their clients
  - Add members 'Int_t fParentIgnoreCnt, fTopItemCnt' that allow
    better tracking of references in view of automatic destruction.
  - Consolidate Has/Num|Children/Parents() methods.

- TEveGeoNode:
  Use TEveElement::HasChildren() instead of checking container size.


git-svn-id: http://root.cern.ch/svn/root/trunk@24147 27541ba8-7e3a-0410-8455-c3a389f83636