OAK-1424 : Oak API allows to create hidden tree and properties

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1570187 13f79535-47bb-0310-9956-ffa450edef68
OAK-1440: o.a.j.o.api.Tree.toString hits hidden nodes
filter hidden items in toString

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1570199 13f79535-47bb-0310-9956-ffa450edef68
OAK-1432 Query: use "union" for complex XPath queries that use multiple "or" (split statements into multiple lines for readability)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1570200 13f79535-47bb-0310-9956-ffa450edef68