* 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.

The previous attempt to use --ethapi as a fallback if --ens-api is not
set does not work because --ens-api has a default value, and also
setting --ens-api to "" is the suggested way to disable ENS lookups.

Signed-off-by: Lewis Marshall <lewis@lmars.net>

This PR adds a Swarm development environment which can be run in a
Docker container and provides scripts for building binaries and running
Swarm clusters.