Merge pull request #66 from nicoruti/pr-external-gcm

External GCM Server + Slow peer timeout
Tracker update, not fully working yet
Merge remote-tracking branch 'origin/master'

Conflicts:
	tracker/src/test/java/net/tomp2p/tracker/TestTrackerRPC.java
fixed testcases for tracker storage
fixing testcases
Improve logging when map is updated