Full candidate release of 0.6.0. This should have all the functionality in, and as many automatic checks in place as we can.

The last couple releases needed minor releases (0.5.1 and 0.5.2) as small errors were made that needed a reissue. So we'll cut a release candidate and have everyone check it. Catalog implementors should have a week to try out the RC and give us any feedback before we finish 0.6.0 If changes are needed we'll do another release candidate.