No longer share global objects from RecoVertex/ConfigurableVertexReco

The classes VertexFitterManager and VertexRecoManager were allowing
code to get access to single instances of  AbstractConfReconstructor and
AbstractConfFitter. This causes thread safety issues. This change
converts the Managers to use factories instead so each caller gets
their own copy. This also solved a memory leak problem in the client
code where sometimes the shared code got the object from a Manager
and sometimes it got it from calling clone(). In the clone() case
the object was never deleted. Now the object is always deleted.