CoreMetadata: update copying constructors to initialize Modulo values
Allow one Modulo annotation of each type for every Image

Previously, only one ModuloZ, ModuloC, and ModuloT was allowed across
the board, which meant that multi-Image datasets could not use a
different Modulo definition for each Image.
Merge pull request #885 from melissalinkert/sdt-annotation

Correctly set Modulo annotations for multi-Image datasets