(bug 30625) Add, to every API upload response, the warnings raised.

(bug 30625) Add, to every API upload response, the warnings raised.

The current API implementation has a parameter for uploads that is
called "ignorewarnings". Currently, it will not only suppress any
warnings from stopping the upload, it will also lose any data from
those warnings.

This patch is sort of on the way to solving Bug 30625, which is in
the UploadWizard extension. That extension needs to know when a file
upload *will* fail, barring a change in some data, in order to make
it easier for a user to fix the foreseeable problems. The solution is
either to fix it this way, or to somehow spoof a file upload, and see
if it succeeds. In the hopes that other extensions will also find
this useful, I opted for the former.

Change-Id: I08b4e29e89ade6cf391ae044fceb788aaba3f5b4