WIP rewrite the daemon

cmd subdir does not build on purpose, it's only left in tree to grab old
code and move it to github.com/zrepl/zrepl/daemon

daemon/serve/serve_tcp.go

@@ -0,0 +1,21 @@
+package serve
+
+import (
+	"github.com/zrepl/zrepl/config"
+	"net"
+)
+
+type TCPListenerFactory struct {
+	Address string
+}
+
+func TCPListenerFactoryFromConfig(c config.Global, in *config.TCPServe) (*TCPListenerFactory, error) {
+	lf := &TCPListenerFactory{
+		Address: in.Listen,
+	}
+	return lf, nil
+}
+
+func (f *TCPListenerFactory) Listen() (net.Listener, error) {
+	return net.Listen("tcp", f.Address)
+}