Terminal: Default profile should be powershell, rather than cmd

[mikemaccana]

@bitcrazed can hopefully back me up here, but cmd is frozen and not getting any more changes, and we generally want people to be using the latest Powershell release.

[miniksa]

ARGH. We meant to do that before pushing this. We were talking about this last week for exactly this reason.

[DHowett-MSFT]

We may also want to follow the Windows Shell option that dictates what shell lives in your WIN+X menu.

[zadjii-msft]

@DHowett-MSFT if that's something we can query, let's please do that.

sponsored by the cmd squad

[mdtauk]

The Windows team should allow read only access to the user's chosen default, so the Terminal can respect that

[binarycrusader]

The registry key set by taskbar settings is:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\DontUsePowerShellOnWinX

The default is 0 to use powershell I believe.

Is it ok to query that?

@zadjii-msft @DHowett-MSFT

[zadjii-msft]

This PR was successfully merged, so I'm closing this issue, and moving discussion of querying the user's default shell to #740