Initial work on friend sync.
get friend names from roster
remove ninvites from client
move constantTimeEquals to lantern-common
Merge branch 'master' into friends
Merge branch 'master' into friends

Conflicts:
	src/main/java/org/lantern/LanternUtils.java
	src/main/java/org/lantern/state/Model.java
ignore friendness for kscope temporarily