Add a keybinding to remove a file from the Nodes tab

[KarlHeitmann]

The Nodes tab has a left panel which has a list of files that have a pattern match.

This issue consists in adding a keybinding so when you have the left panel selected, you can hit eg "r" key, and it will remove the selected file from the list.

This is useful in case you are exploring your codebase, you have a lot of matches, and you want to narrow down the list of files to do your exploration.