Overlink support 1.0

[JustinPrivitera]

Finished the last few things needed for Overlink support:

• require matsets to be present to write overlink
• convert data arrays to doubles since overlink does not support floats
• remove warning saying overlink is not fully supported
• update tests to add matsets where needed to make overlink save happy
• verified that all files we write to overlink in tests pass Jeff's overlink file format validator