Wharfie

Actually it seems as tar has still problems with it. I can't avoid that tar thinks that s.th. is renamed, even if it is not.
In my tests I found no problems, except the warning from tar until now. But I added it as a command line option anyway, to be safe.

By-the-way I fixed the handling of files in ADD a bit.
- URLs are supported now
- Implicite makerules don't interfer anymore with ADD