GeoModelKernel streamline classes

• GeoGraphNode: Do not change it w.r.t what's in main. We only need the parent for the fetching of the transforms
• GeoPlacement: Move the parent method here
• GeoVPhysVol: The handling of the child tree is implemented in GeoFullPhysVol & GeoPhysVol. I'd say that this is code duplication
• GeoPositionCacheNode: Template the class over the later usecase. The specified template will be later used to communicate with the GeoAlignmentStore. Remove the virutal function calls & Implement the changes from !314 (closed) w.r.t. transform retrieval.

Tagging: @boudreau, @tsulaia

GeoModelCore/GeoModelHelpers/GeoModelHelpers/getChildNodesWithTrf.h

@@ -32,8 +32,15 @@ struct GeoChildNodeWithTrf {
         GeoChildNodeWithTrf(GeoVolumeCursor& curs);
 };
 
+/*** @brief Returns all direct children of a volume with their transform. Equicalent volumes can be summarized.
+ *          In this case, the inductionRule transform to move from one copy to the next, is non-trivial
+*/
 std::vector <GeoChildNodeWithTrf> getChildrenWithRef (PVConstLink physVol,
                                                       bool summarizeEqualVol = true);
+/**** @brief Traverses through the GeoVPhysVol tree and returns all sub volumes of this tree.*/
+std::vector<GeoChildNodeWithTrf> getAllSubVolumes(PVConstLink physVol);
+
+
 
 /**
  *  Returns whether a volume has fullPhysical volume nodes in