Merge pull request #3 from HBOCodeLabs/master

Supporting command prefix semantics
improved prefix command ui
use lombok in PrefixCommandPair
add command issue to YouTrack command tab
[maven-release-plugin] prepare release youtrack-plugin-0.6.0-beta1
[maven-release-plugin] prepare for next development iteration
[maven-release-plugin] prepare release youtrack-plugin-0.6.0-beta2
[maven-release-plugin] prepare for next development iteration