Merge changes in the 2.4 branch into the trunk for the ORNL Mercury schema support. References https://projects.ecoinformatics.org/ecoinfo/issues/6619.
This schema is maintained by Jim Green (jgreen@iiaweb.com) and Ranjeet Devarakonda (devarakondar@ornl.gov). The schema uses a subset of the FGDC 1998 CSDGM elements, along with custom elements specific to the Mercury Metadata web application. Support is included in Metacat for Coordinating Node operations in the DataONE network.
Add the three Darwin Core schemas required by the Dryad Metadata Profile (via imports).
Add cached versions of the DataONE, Dryad, Dublin core, and Darwin Core schemas to Metacat. Remove schemaLocation attributes so that we rely on the local catalog and don't use (potentially changing) URL endpoints.