Replace riddler with code that constructs config.json directly

Generated largely from the specified config; small parts taken from `docker image inspect`,
such as the command line.

Renamed some of the yaml keys to match the OCI spec rather than Docker Compose as
we decided they are more readable, no more underscores.

Add some extra functionality
- tmpfs specification
- fully general mount specification
- no new privileges can be specified now

For nostalgic reasons, using engine-api to talk to the docker cli as
we only need an old API version, and it is nice and easy to vendor...

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

vendor/github.com/docker/go-connections/sockets/sockets.go

@@ -0,0 +1,38 @@
+// Package sockets provides helper functions to create and configure Unix or TCP sockets.
+package sockets
+
+import (
+	"errors"
+	"net"
+	"net/http"
+	"time"
+)
+
+// Why 32? See https://github.com/docker/docker/pull/8035.
+const defaultTimeout = 32 * time.Second
+
+// ErrProtocolNotAvailable is returned when a given transport protocol is not provided by the operating system.
+var ErrProtocolNotAvailable = errors.New("protocol not available")
+
+// ConfigureTransport configures the specified Transport according to the
+// specified proto and addr.
+// If the proto is unix (using a unix socket to communicate) or npipe the
+// compression is disabled.
+func ConfigureTransport(tr *http.Transport, proto, addr string) error {
+	switch proto {
+	case "unix":
+		return configureUnixTransport(tr, proto, addr)
+	case "npipe":
+		return configureNpipeTransport(tr, proto, addr)
+	default:
+		tr.Proxy = http.ProxyFromEnvironment
+		dialer, err := DialerFromEnvironment(&net.Dialer{
+			Timeout: defaultTimeout,
+		})
+		if err != nil {
+			return err
+		}
+		tr.Dial = dialer.Dial
+	}
+	return nil
+}