Add ExecFunction.GetProcessStartInfo methods.

[tmds]

These methods enable obtaining the ProcessStartInfo so it can be passed to start a Process at a later time.

Fixes #23

cc @davidfowl

[tmds]

@davidfowl I'll release this to nuget.org on Friday.
If you want to give it a try using the CI version, you can find it at:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="tmds" value="https://www.myget.org/F/tmds/api/v3/index.json" />
  </packageSources>
</configuration>

[tmds]

This is part of 0.7.0 which was just published to nuget.org.

[tmds]

There was a bug in the VS debugger integration in 0.7.0. If you care about that working, you need to use 0.7.1.