OAK-4265 XPath: support limited form of union
OAK-4265 XPath: support limited form of union

git-svn-id: 67138be12999c61558c3dd34328380c8e4523e73@1763760 13f79535-47bb-0310-9956-ffa450edef68

davidegiannella/jackrabbit-oak,davidegiannella/jackrabbit-oak,davidegiannella/jackrabbit-oak,davidegiannella/jackrabbit-oak,davidegiannella/jackrabbit-oak