Activator performance improvement

Shouldn't close the previous PR early. Turns out I did not have to change much of my design.

Pinging previous trackers
@pranavkm
@halter73 
@rynowak
@ipjohnson
@yishaigalatzer 
So I have removed the extra non-varargs extra method from the interface. Actually according to my micro-benchmark it  caused 15% regression for the non-varargs calls.

If we ever need to squeeze a little more performance this is one place we can look at.