rpc rewrite: control RPCs using gRPC + separate RPC for data transfer

transport/ssh: update go-netssh to new version
    => supports CloseWrite and Deadlines
    => build: require Go 1.11 (netssh requires it)

transport/fromconfig/transport_fromconfig.go

@@ -0,0 +1,58 @@
+// Package fromconfig instantiates transports based on zrepl config structures
+// (see package config).
+package fromconfig
+
+import (
+	"fmt"
+	"github.com/pkg/errors"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/transport"
+	"github.com/zrepl/zrepl/transport/local"
+	"github.com/zrepl/zrepl/transport/ssh"
+	"github.com/zrepl/zrepl/transport/tcp"
+	"github.com/zrepl/zrepl/transport/tls"
+)
+
+func ListenerFactoryFromConfig(g *config.Global, in config.ServeEnum) (transport.AuthenticatedListenerFactory,error) {
+
+	var (
+		l transport.AuthenticatedListenerFactory
+		err error
+	)
+	switch v := in.Ret.(type) {
+	case *config.TCPServe:
+		l, err = tcp.TCPListenerFactoryFromConfig(g, v)
+	case *config.TLSServe:
+		l, err = tls.TLSListenerFactoryFromConfig(g, v)
+	case *config.StdinserverServer:
+		l, err = ssh.MultiStdinserverListenerFactoryFromConfig(g, v)
+	case *config.LocalServe:
+		l, err = local.LocalListenerFactoryFromConfig(g, v)
+	default:
+		return nil, errors.Errorf("internal error: unknown serve type %T", v)
+	}
+
+	return l, err
+}
+
+
+func ConnecterFromConfig(g *config.Global, in config.ConnectEnum) (transport.Connecter, error) {
+	var (
+		connecter transport.Connecter
+		err       error
+	)
+	switch v := in.Ret.(type) {
+	case *config.SSHStdinserverConnect:
+		connecter, err = ssh.SSHStdinserverConnecterFromConfig(v)
+	case *config.TCPConnect:
+		connecter, err = tcp.TCPConnecterFromConfig(v)
+	case *config.TLSConnect:
+		connecter, err = tls.TLSConnecterFromConfig(v)
+	case *config.LocalConnect:
+		connecter, err = local.LocalConnecterFromConfig(v)
+	default:
+		panic(fmt.Sprintf("implementation error: unknown connecter type %T", v))
+	}
+
+	return connecter, err
+}