Update docs to reflect using the openstack-juju cmd

Patch for changing that command next.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
rename bin/openstack to bin/openstack-juju

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
More documentation

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>