* New UploadFromUrlJob class to handle Upload-by-Copy

* New UploadFromUrlJob class to handle Upload-by-Copy
* Define variable for ApiUserrights.php that wasn't defined before.
* Add convertVerifyErrorToStatus and getVerificationErrorCode to
  UploadBase to translate error consts since UploadFromUrl will
  need a message to display to end-users.
* refactor mime-checking out of UploadBase::verifyFile into
  UploadBase::verifyMimeType
* Make UploadBase::verifyFile always return arrays for errors
* Use HttpFunctions instead of custom curl handler for async downloading
* TODO: Need a way to feed errors back to the requestor
* TODO: Need to add watchlist param handling and warnings checks.