JCR-3551: DavEx cannot handle Double.NaN properties. The DavEx server now sendsNaN and Infinity as type-hinted strings and spi2devex sends them as parts.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/branches/2.6@1468173 13f79535-47bb-0310-9956-ffa450edef68