added contextual privateCreators dico to ParsedDicomFile -> this allows you not to have to define a DefaultPrivateCreator. This was tested only in the scope of C-Find requests but should not have impact on other parts since it is not used out of C-Find right now

# This is the list of the symbols that must be exported by Orthanc
# plugins, if targeting OS X

_OrthancPluginInitialize
_OrthancPluginFinalize
_OrthancPluginGetName
_OrthancPluginGetVersion