Pull in upstream changes and create a manifest for desktop b2g

We'll be running gaia-ui-tests against desktop b2g in place of the pandas, and we'd like to start with a green set of tests, updating the manifest as we fix more tests to run green. 

This is the starting manifest. It's needed by tbpl so we can start running green gaia-ui-tests on our Cedar branch (https://tbpl.mozilla.org/?tree=Cedar), and once green there, we can run them on other branches.