OAK-1861: Limit memory usage of DocumentNodeStore.readChildren()

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1606638 13f79535-47bb-0310-9956-ffa450edef68
OAK-1804 TarMK compaction
 - docs

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1606639 13f79535-47bb-0310-9956-ffa450edef68