implement local replication using new local transport

The new local transport uses socketpair() and a switchboard based on
client identities.
The special local job type is gone, which is good since it does not fit
into the 'Active/Passive side ' + 'mode' concept used to implement the
duality of push/sink | pull/source.

daemon/connecter/connect_local.go

@@ -0,0 +1,26 @@
+package connecter
+
+import (
+	"context"
+	"fmt"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/daemon/serve"
+	"net"
+)
+
+type LocalConnecter struct {
+	clientIdentity string
+}
+
+func LocalConnecterFromConfig(in *config.LocalConnect) (*LocalConnecter, error) {
+	if in.ClientIdentity == "" {
+		return nil, fmt.Errorf("ClientIdentity must not be empty")
+	}
+	return &LocalConnecter{in.ClientIdentity}, nil
+}
+
+func (c *LocalConnecter) Connect(dialCtx context.Context) (conn net.Conn, err error) {
+	switchboard := serve.GetLocalListenerSwitchboard()
+	return switchboard.DialContext(dialCtx, c.clientIdentity)
+}
+