2.0.0 Release Candidate 3

The primary change to this release is the new provenance editor - an
easy-to-use tool scientists can use to document how their data is
created by linking together data sources, derivations, and code.

Includes many stability improvements to the new metadata editor.

Ready to be used with production catalogs in Beta.

For a complete list of changes, see https://github.com/NCEAS/metacatui/milestone/16