Merge pull request #262 from xuzhang/dev

fix bug TDIS-6430
added onremoved listener check
[Contact] Resolve the TypeMismatchError issue.

* [NABI-RSA] TDIS-5908, TDIS-5812
Merge pull request #266 from wcwang/next

[Contact] Resolve the TypeMismatchError issue.
[Download] reimplement function _checkDownloadParamters

* allow attibute of callback don't exist
[Download] fix bug on type of size

* the totalsize of download should be a number not a string
[Download] add some urls into cache

* In order to pass QA's test, we add some urls from tests set to
  download cache
[Download] reimplement setListener() function
[Download] fix bug on cancel() function

* The state to cancel can be Downloading or Paused. The root casue
  of issue is that it ignore Paused state.