send the intent build before via broadcast instead of an anonymous one.
moved changing of the button label from OnCreate to onReceive. 
That's possible (and necessary now) because the Start, Stop, and change
events are now sent by the DistanceService via sendBroadcast.
This eliminates the need to set the label in two different places
(clicking the button and receiving events from service)

Saving the log can now only be done by clicking on the Button while it
displays the "Save Log" text.