Feature Request: Add ability to arbitrarily remove matches from results buffer

[amodelbello]

Sometimes after a search there's a lot of unneeded results that aren't easily filtered out using a regex or file type. It would be really nice to be able to simply select them as a region and remove/hide them.

Additionally it would be very useful to fold results by file.

[dajva]

Have a look at #132 for enabling outline mode.