Fix json/base64 encode and decode to use top-level functions.

[lrhn]

Please add translations:

JSON.encode -> jsonEncode
JSON.decode -> jsonDecode
BASE64.encode -> base64Encode
BASE64.decode -> base64Decode

Converting the first one to json.encode causes a lot of conflicts with code like:

var json = JSON.decode(input);

and it's a simple change.