OAK-2000 Observation events accessibility not checked correctly
 - merged 1614344,1614345,1614591,1614604



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1637659 13f79535-47bb-0310-9956-ffa450edef68
OAK-2254 Observation events accessibility check should respect session refresh settings
 - merged rev r1637368



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1637663 13f79535-47bb-0310-9956-ffa450edef68
OAK-2256: MemoryNodeBuilder NPE on base() following root refresh
 - merged r1637413



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1637664 13f79535-47bb-0310-9956-ffa450edef68
OAK-2218 Allow SegmentNodeBuilder to provide child builders of the same type
 - merged r1633697,r1633768



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