Refactor node ID handling, use check digits (fixes #269)

New node ID:s contain four Luhn check digits and are grouped
differently. Code uses NodeID type instead of string, so it's formatted
homogenously everywhere.

cid/cid_test.go

@@ -4,28 +4,35 @@
 
 package cid
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/calmh/syncthing/protocol"
+)
 
 func TestGet(t *testing.T) {
 	m := NewMap()
 
-	if i := m.Get("foo"); i != 1 {
+	fooID := protocol.NewNodeID([]byte("foo"))
+	barID := protocol.NewNodeID([]byte("bar"))
+
+	if i := m.Get(fooID); i != 1 {
 		t.Errorf("Unexpected id %d != 1", i)
 	}
-	if i := m.Get("bar"); i != 2 {
+	if i := m.Get(barID); i != 2 {
 		t.Errorf("Unexpected id %d != 2", i)
 	}
-	if i := m.Get("foo"); i != 1 {
+	if i := m.Get(fooID); i != 1 {
 		t.Errorf("Unexpected id %d != 1", i)
 	}
-	if i := m.Get("bar"); i != 2 {
+	if i := m.Get(barID); i != 2 {
 		t.Errorf("Unexpected id %d != 2", i)
 	}
 
 	if LocalID != 0 {
 		t.Error("LocalID should be 0")
 	}
-	if i := m.Get(LocalName); i != LocalID {
-		t.Errorf("Unexpected id %d != %c", i, LocalID)
+	if i := m.Get(LocalNodeID); i != LocalID {
+		t.Errorf("Unexpected id %d != %d", i, LocalID)
 	}
 }