Core adaptations

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
Fill out generic postCmd endpoint
Implement 'docker nets [ls]'

Conflicts:
	net/net.go
Disable job stderr output for now
Implement 'docker nets create'

Conflicts:
	net/net.go
Implement 'docker nets rm'

Conflicts:
	net/net.go
Implement join and leave

Conflicts:
	net/net.go