Moved classes from reddav.php into own files.

Finished moving classes out from include/reddav.php into own files. Also
continued with namespace for RedDAV.
Improved some docs and added some todos and fixmes.
A fix, but I have no case to verify.

I could not find out under which conditions this is relevant and therefore have no test case, but it must be of instance RedDAV\RedFile.
Merge pull request #636 from dawnbreak/RedDAV

Moved classes from reddav.php into own files.