add sequential access for json object
(cherry picked from commit 81446430e943ca80e71330171f60c332c91971cf)
add keyAt for wyJSONObject
(cherry picked from commit d622acd5aa14c7d37d8800c57ffb6761ed2dfdde)
change vector pointer to vector
(cherry picked from commit ab9786c0c4c33b0076dcac739f6b6e83be8aa86d)