OAK-1190: Limit size of batch update in background write

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1547017 13f79535-47bb-0310-9956-ffa450edef68
OAK-98 Source code formatting, code conventions, Javadocs

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1547018 13f79535-47bb-0310-9956-ffa450edef68