Allow to show multiple panels at the same time (split pane)

[drgullin]

• VSCode Version: 1.5.1
• OS Version: OS X El Capitan

While there's a double pane for files, an errors/terminal board can't be divided into two panes right now. This would be very helpful, since terminal and errors are usually needed together - you type some code and see compilation notes in terminal. Most of the time there's too much whitespace at the right side of the terminal/errors board, so we can add same double-pane toggle icon [ | ] at the right side of the board and make it work:

• if double-pane mode is switched on and one side is empty, then, we would add a terminal/errors board right there
• if double-pane mode is switched off, then, make visible only left board, right one should disappear
• if one of the boards is switched off using hotkey, then, remove it and make a board single-pane (if there's one board in double-pane - remove both panes)

[DmitryEfimenko]

I think there should be a way to split terminal window independently of the amount of code windows.

[drgullin]

@bpasero any progress on this issue?

[bpasero]

No, this is something we are not working on currently nor planning short term.

[stealthybox]

Duplicate of #10546
There's movement on this.

edit:
just to clarify, it doesn't have the same reactive behavior that's described here, but it's related