Double-click on find in files results should add file to the working set

[jasonsanjose]

Currently, single or double clicking a "find in files" result opens the file in an editor without adding the file to the working set. The single click behavior is consistent with the project tree.

[njx]

Marking "to user story" for official Find in Files story.

[pthiess]

Added to Trello card 266

[njx]

Note that #3151 has a fix for this.

[TomMalbran]

I added the double click to move to working set in the second part of my pull request in #4303. So it might get into master sooner.

[jasonsanjose]

Confirmed in Sprint 34. Thanks @TomMalbran.