filtering: refactor; change API; add "filters_update_interval" setting

+ config: "filters_update_interval"
* add /control/filtering_info
* remove /control/filtering/enable
* remove /control/filtering/disable

* add /control/filtering_config
* remove /control/filtering/status

* add /control/filtering/set_url
* remove /control/filtering/enable_url
* remove /control/filtering/disable_url

querylog/querylog.go

@@ -10,14 +10,20 @@ import (
 
 // QueryLog - main interface
 type QueryLog interface {
+	// Close query log object
 	Close()
 
 	// Set new configuration at runtime
 	// Currently only 'Interval' field is supported.
 	Configure(conf Config)
 
+	// Add a log entry
 	Add(question *dns.Msg, answer *dns.Msg, result *dnsfilter.Result, elapsed time.Duration, addr net.Addr, upstream string)
+
+	// Get log entries
 	GetData() []map[string]interface{}
+
+	// Clear memory buffer and remove log files
 	Clear()
 }
 
@@ -27,7 +33,7 @@ type Config struct {
 	Interval uint32 // interval to rotate logs (in hours)
 }
 
-// New - create instance
+// New - create a new instance of the query log
 func New(conf Config) QueryLog {
 	return newQueryLog(conf)
 }