OAK-2286 - merged to branch 1.0

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1641342 13f79535-47bb-0310-9956-ffa450edef68
OAK-2271 Compaction estimation time should not depend on number of checkpoints
 - merged r1641352



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1641358 13f79535-47bb-0310-9956-ffa450edef68