OAK-593: Segment-based MK

Another simple optimization. Nodes with different templates can't be equal.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1446585 13f79535-47bb-0310-9956-ffa450edef68
OAK-533 - Define behaviour for and implement mix:lastModified
	- for any subgraph change of a node with the mixin mix:lastModified (including changes to the node's own properties),
	the jcr:lastModified and jcr:lastModifiedBy properties are automatically updated in a commit hook