Moved RedBrowser class from reddav.php to it's own file.

First step on cleaning up ReadDAV classes and restructuring it bit in
preparation for adding some more DAV features, photo access, CalDAV, etc.
and hopefully also some PHPunits.
Add a PHP5.3 namespace for RedDAV classes. Any objections against this or
the vendor namespace?
Add some more documentation for RedBrowser.