* swarm/api: url scheme bzz-list for getting list of files from manifest

Replace query parameter list=true for listing all files contained
in a swarm manifest with a new URL scheme bzz-list.

* swarm: replaace bzzr and bzzi schemes with bzz-raw and bzz-immutable

New URI Shemes are added and old ones are deprecated, but not removed.
Old Schemes bzzr and bzzi are functional for backward compatibility.

* swarm/api: completely remove bzzr and bzzi schemes

Remove old schemes in favour of bzz-raw and
bzz-immutable.

* swarm/api: revert "completely remove bzzr and bzzi schemes"

Keep bzzr and bzzi schemes for backward compatibility. At least
until 0.3 swarm release.