Fix #579

1. Added --workdir command-line argument that lets configure the working dir.
2. Made "dnsforward" use this workdir parameter when saving/reading querylog.
3. Reworked "dnsforward" -- moved http handlers out of there to control.go

filter.go

@@ -251,5 +251,5 @@ func (filter *filter) load() error {
 
 // Path to the filter contents
 func (filter *filter) Path() string {
-	return filepath.Join(config.ourBinaryDir, dataDir, filterDir, strconv.FormatInt(filter.ID, 10)+".txt")
+	return filepath.Join(config.ourWorkingDir, dataDir, filterDir, strconv.FormatInt(filter.ID, 10)+".txt")
 }