Fix #371 #421

Filters are now saved to a file
Also, they're loaded from the file on startup
Filter ID is not passed to the CoreDNS plugin config (server-side AG DNS must be changed accordingly)
Some minor refactoring, unused functions removed

coredns_plugin/coredns_plugin_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/miekg/dns"
 )
 
+// TODO: Change tests -- there's new config template now
 func TestSetup(t *testing.T) {
 	for i, testcase := range []struct {
 		config  string