Disallow sending selection to terminal when in a notebook editor cont…

[IanMatthewHuff]

…ext to not mess with shift-enter execution

microsoft/vscode-jupyter#328

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[IanMatthewHuff]

Hey Python folks. Had a change to your package.json proposed from the Jupyter side of things.

By default, notebooks use shift+enter to execute a notebook cell. In the new notebook UI this keybinding is directly owned by the VS Code team. By default if customers don't have the jupyter.ownsSelection setting on (this is the old setting to juggle shift+enter sending to the interactive window versus the terminal) then the Python send to terminal keybinding wins out and instead of the cell executing it sends just that line to the terminal, which we've been having native notebook users complain about already.

This isn't what customers expect, so I added to the when clause here to make execSelectionInTerminal not apply when the the editor focus is in a notebook editor. This key context is from the VS Code team, not the Jupyter extension so it will disallow this for all notebook editors. I believe this is what customers would expect by default and they could edit the keybinding if customers would like to still send chunks of notebook cells to the terminal. Can loop in PMs on this as well if we are worried about that scenario.