Supporting command prefix semantics

This does a few things:
* Adds Lombok to some classes that benefit from those patterns
* Adds support for prefixing commands to issue references, so a commit message can say "Fixes #PROJ-123" rather than the more obtuse "#PROJ-123 State Fix"
* Adds the commit SHA to the implicit "Related to build" comment. When Github is properly configured for the project it will turn into a link in YouTrack's UI.
* Makes it so the implicit comment that follows a commit can be multiline.
* Adds tests around new functionality.

Please let me know if there's anything in this that doesn't make sense or shouldn't be merged. Feedback is appreciated.

The way the prefix commands are exposed in the UI is definitely suboptimal. If anyone can help with making that better I'd like to fix that before merging, but for my own purposes what's there is okay.