illegal format for WebDAV lock tokens

WebDAV lock tokens are URIs, while JCR lock tokens aren't. Therefore, the WebDAV servlet needs to transform outgoing JCR lock tokens (response headers and WebDAV properties) into URI format, and needs to parse the original lock token out of incoming WebDAV lock tokens (in request headers).

Proposed mapping:

• when the JCR lock token uses UUID format, use "urn:uuid",

• otherwise encode with a constant prefix, such as "tag:jackrabbit.apache.org,2008:LockTokens."