[test] new metadata related fixes
[depmap] new metadata related changes

currently broken...
[prov] new metadata experiment #1
[artifact] new metadata related changes

currently broken
[depmap] Add compressed metadata support back
[artifact] Fix a typo
[depmap] Move import into proper place
[artifact] Go back to using simple init

Add separate from_metadata classmethod instead and use it
[depmap] Fix up a few typos
[artifact] Add partial support for compatVersions

Not all methods support this. In some cases it's probably not needed/wanted
anyway
[artifact] Properly initialize values when creating from metadata
[artifact] Handle incomplete metadata properly
[depmap] Fix java nad javadevel requires methods for new metadata
[test] Fix up part of depmap tests
[artifact] Do not compare against None

compatVersions can be empty array but that still means non-compat. Just return
the data and let clients compare(usually only as boolean)
[test] Fix expected data for compressed metadata
[test] Fix multiple namespace metadata test
[data] Move requiresJava property to global namespace
[artifact] Add support for equality check

This means we Artifacts will work correctly in sets
[depmap] Properly deduplicate required artifacts