make sample more user-friendly

Add a text prompt that tells the user of the sample what they need to do
next.

Let the user specify when they want to stop recording, instead of
forcing them to wait five seconds every time.
Fix (apparently harmless) error

Whenever I debug unity from MonoDevelop, it would show an error
indicating that it couldn't load a project file. While the error was
apparently harmless, it could confuse customers. This checkin removes
the error.