Options controlling run behavior

We should add support for the following MSBuild properties to control how 'dotnet run' behaves:

* `WaitForExit`: if 'dotnet run' should return when the app is launched, or wait for the app to exit before returning.
* `StandardOutputPath`: a path to where stdout from the app is written to. If `WaitForExit=true`, this will be stdout by default.
* `StandardErrorPath`: same for stderr.