[NX-548] bring back xml-based capability storage, copied from 2.7 and adapted to latest api changes.
[NX-548] Add conversion from KZ -> XML.  Update support-zip integration to include the xml file again.
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Merge pull request #612 from sonatype/NX-548-revert-kz-capabilities

REVIEW: [NX-548] (2.9) revert kz capabilities