Open file dialog should start in the directory for the current active file

[DanielRosenwasser]

When using File > Open File, this will open the directory of the last file selected through File > Open File. This is sub-optimal, since the current active file may not have been opened through that dialog. The dialog itself should be context-aware.

[egamma]

@bpasero fyi

[bpasero]

Not convinced, but Sublime seems to do this too.

[sfortiner]

Definitely would like this behavior.

[DanielRosenwasser]

Yeah, Visual Studio and Notepad++ do this as well.

I was looking into this, but I backed off because I wasn't sure how to appropriately make windows depend on their contained editors (or whether it would even be appropriate to do so). If you guys had any guidance on it, I'd be glad to work on it.

[bpasero]

Pushed for opening files. I left this untouched for Mac because imho this does not make sense for opening folders.