Dictionaries needed for ROOT 6

In ROOT6, dictionaries are needed for classes ora::Reference and ora::NamedReference, even though these classes are not persisted.  The absence of these dictionaries causes step 4 of relval test 1001 to fail.
This pull request adds these dictionaries to CondCore/ORA.  Note that these dictionaries were also needed in ROOT 5, but only for the CondCore/ORA unit tests.  Since these dictionaries will now be in CondCore/ORA itself, they no longer are needed in CondCore/ORA/test, as these would be duplicate definitions.
Note that this pull request is not sufficient to make step 4 of relval 1001 run successfully , because with this pull request, the test fails later for a different reason. Please merge promptly.