Fixed a bug for periodic discoveries. 
It seems that BTManagerThread has no more bugs regarding the logic of
discoveries

Changed the way to calculate CPU usage. It looks quite realistic now.
	The change has only been an increase from a few milliseconds to a
second between the readings done to the /proc/stat file.
	Original function:
https://stackoverflow.com/questions/3118234/get-memory-usage-in-android

	
Changed the "Set plan" button to "Set plan & start test"