Add the methods Dict:AddDict(fullPathPrivateDictionaryFileName)

Add the methods Dict:AddDict(fullPathPrivateDictionaryFileName)
 and Dict::RemoveDict(fullPathPrivateDictionaryFileName)
 to allow user to choose the 'Private Dictionary' he wants to work with.
One can dream about a better API;
This one allow right now anybody to see very easyly
if the use of a given private dicom dictionary is of any help or not.