Support access to working trees through remote transport

Especially in web development, changes are often applied directly to the application, which resides on an ftp server. As it often isn't possible to install bzr directly on this server, remote access through bzr would make life easier.
Needed operations on ftp that are not yet supported
- push (With changes to working tree)
- commit & status (For changes made by 3rd parties that access the ftp directly in some project)