Make command async, improve output buffer behavior

Sorry for the mega pull, feel free to pick just the commits you want

* Async launching to avoid blocking
* Keep previous results in output screen (like default find behavior)
* Clean up output view (mark as scratch, hide line numbers)
* Make quick panel monospace
* Add syntax highlighting to output results to show line numbers
  * matches xml, json, and plain output formats
* Add double-click jump-to support
  * fires on selection change of a line containing a reference
  * matches xml, json, and plain output formats