Improve files table UX (fixes #121):

[jpovixwm]

• Add visual indication to deselected directories with selected subrows
• Automatically deselect directories whenever their children are deselected
• Automatically select directories as soon as all of their children are selected
• Change Ctrl-A behavior so that it only selects entries that match the entered search terms
• Deselect entries that become hidden while using the search bar

Fair warning: this makes the issue with not being able to perform the context menu actions "Open" and "Open folder", when multiple entries are selected, just a tiny bit worse for single-file directories, because when you right click the file, the directory gets automatically selected. When it comes to my opinion on how to fix that, I think it'd be OK to make these context menu entries apply only to the row that was actually right-clicked.

[jpovixwm]

Uh oh, looks like the "Open" and "Open folder" actions are broken for single-file torrents too. I'll investigate tomorrow.

[qu1ck]

Thanks for the fix.