OAK-593: Segment-based MK

Initial segment-based node and property state implementations.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1444166 13f79535-47bb-0310-9956-ffa450edef68
OAK-593: Segment-based MK

Implement iteration over all entries in a map record

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1444167 13f79535-47bb-0310-9956-ffa450edef68