Used Timer0 for LED blinking instead of Timer3
Removed obsolete project paths
Passed parameters to playxxx functions
Renamed LED to ACTIVITY_LED
Update handling of playback interruption by user
Fix the "user abort" button press logic.

When the user requests to abort the playback by pressing the button
the code now waits for any button press bouncing to subside, then
it waits for the user to release the button, then waits for any
button release bouncing to subside.