accounts/abi: satisfy most of the linter warnings

+ adding missing comments
+ small cleanups which won't significantly change
  function body.
+ unify Method receiver name

accounts/abi/pack.go

@@ -48,9 +48,8 @@ func packElement(t Type, reflectValue reflect.Value) []byte {
 	case BoolTy:
 		if reflectValue.Bool() {
 			return math.PaddedBigBytes(common.Big1, 32)
-		} else {
-			return math.PaddedBigBytes(common.Big0, 32)
 		}
+		return math.PaddedBigBytes(common.Big0, 32)
 	case BytesTy:
 		if reflectValue.Kind() == reflect.Array {
 			reflectValue = mustArrayToByteSlice(reflectValue)