Nexus Kenai Realm Plugin.

While this realm is not shipped with any of distros
it's OSS plugin for Nexus, hence it built with Nexus OSS.
Merge remote-tracking branch 'origin/master' into nexus-kenai-plugin
Moved in Kenai Realm into Nexus Kenai plugin
Codified the testing wiki.

This is simple IT that actually drives nexus-kenai-plugin
(with a mock Kenai server) and verifies logging in and corresponding
role mapping works with Kenai realm.
Cleanup.

Javadoc, since tags, imports...
Missing XML license header
Making Kenai AuthAPI Behaviour more correct.

By specs, it should respond to POST only.
Merge remote-tracking branch 'origin/master' into nexus-kenai-plugin
Merge pull request #839 from sonatype/nexus-kenai-plugin

Nexus Kenai Realm Plugin