Implement blackbox in Golang (#250)

* Initial release

pkg/bblog/bblog.go

@@ -0,0 +1,48 @@
+package bblog
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+)
+
+/*
+
+To use this, include the following lines in your .go file.
+
+var logErr *log.Logger
+var logDebug *log.Logger
+func init() {
+  logErr = bblog.GetErr()
+  logDebug = bblog.GetDebug(debug)
+}
+
+Or in a function:
+
+  logErr := bblog.GetErr()
+  logDebug := bblog.GetDebug(debug)
+	logDebug.Printf("whatever: %v", err)
+
+*/
+
+var logErr *log.Logger
+var logDebug *log.Logger
+
+// GetErr returns a logger handle used for errors
+func GetErr() *log.Logger {
+	if logErr == nil {
+		logErr = log.New(os.Stderr, "", 0)
+	}
+	return logErr
+}
+
+// GetDebug returns a Logger handle used for debug info (output is discarded if viable=false)
+func GetDebug(visible bool) *log.Logger {
+	if visible {
+		logDebug = log.New(os.Stderr, "", 0)
+	} else {
+		// Invisible mode (i.e. display nothing)
+		logDebug = log.New(ioutil.Discard, "", 0)
+	}
+	return logDebug
+}