OAK-593: Segment-based MK

Refactor the Record classes to take the SegmentReader as
an argument instead of keeping an internal reference to it.
This makes them more lightweight and allows RecordId to
be merged into Record and thus SegmentWriter to return full
Record instances instead of just RecordIds.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1443449 13f79535-47bb-0310-9956-ffa450edef68
OAK-593: Segment-based MK

Call reader directly in record methods

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1443450 13f79535-47bb-0310-9956-ffa450edef68