Close Open Documents from folder when closing folder

[franciol]

Fixes #576
FileView sends a signal to MainWindow so it can verify if there's an open file from that folder.
MainWindow then closes all docs open from that folder.

[jeremypw]

Thanks for your first contributon to Code!

This works OK for the simple case where there is one view and it has documents in it and the approach makes sense. However, there are issues with some corner cases as noted inline.

• If there is a split view and the wrong view is focused then the project folders do not get closed
• If there are no documents open and the welcome view is showing then closing a project folder produces a spurious blank view.

[jeremypw]

@franciol I have noticed that there seems to be another previous open PR addressing the same issue - #782. Your approach seems simpler though, so if you can fix the outstanding issues and if no disadvantages of your approach come to light, I would prefer it.

[jeremypw]

This works well now. I will approve but leave unmerged pending review from @tintou.

[jeremypw]

@tintou Do have any comments for this?

[jeremypw]

Seems to have acquired a build - problem - investigating.

[jeremypw]

@franciol This PR needs updating due to changes in master (which merging did not fix). split_view no longer exists.

Are you in a position to return this PR to working order?

[jeremypw]

Closed in favour of #912