Moving the wait time for rapid refresh scenarios

- Move the notification of project changed to happen before the compilation
 instead of after.
- Return the list of sources files to the runtime so that it can watch files.
This allows the runtime (for certain changes) to shutdown faster than
VS can tell the DTH that anything changed.

/cc @DamianEdwards @PradeepKadubandi @BillHiebert 

It might be worth looking into the time it takes to receive the message when it originates from VS. I couldn't get it fast enough just relying on the DTH communication.