OAK-593: Segment-based MK

Node templates. The size of a basic ACL with four ACEs comes down from 631 bytes to 394 bytes, amortized to 140 bytes.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1445999 13f79535-47bb-0310-9956-ffa450edef68