Deprecate obsolete capabilities related support classes and use the ones copied from pluginkit

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Revert wrongly removed functionality from p2 aggregator capability

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge pull request #117 from sonatype/use-pluginkit-copied-classes

TRIVIAL: Implement OSS capabilities using capabilities related support classs moved from pluginkit
Merge remote-tracking branch 'origin/master' into nexus-5790-new-content-impl