multi queues allow different queues run async but same queue run one by one

[caoglish]

feature

1. can define multi queue
2. different queue run async
3. same queue run in one by one

one more parameter

$.ajaxQueue(ajaxOpts,queueIndex)//queueIndexdefine which queue will be used.

queueIndex default value is 0(use 0th queue as default). if use single queue only, this parameter can be ignored. So it should not be impact previous API.