all: implement reload command

This commit adds reload command to ctrld for re-fetch new config from
ContorlD API or re-read the current config on disk.

cmd/cli/reload_windows.go

@@ -0,0 +1,18 @@
+package cli
+
+import (
+	"errors"
+	"os"
+	"time"
+)
+
+func notifyReloadSigCh(ch chan os.Signal) {}
+
+func (p *prog) sendReloadSignal() error {
+	select {
+	case p.reloadCh <- struct{}{}:
+		return nil
+	case <-time.After(5 * time.Second):
+	}
+	return errors.New("timeout while sending reload signal")
+}