Alter the way Companion Updates Happen – Use Push

The AI Client code (in the browser) now downloads the new
Companion (from the service) and “pushes” it to the Companion using a
mechanism similar to the mechanism used to send assets to the
Companion. This eliminates difficulties encountered when a proxy
exists between the Internet and the AI user’s location.

Change-Id: I5d91de137d2ed57199949b0761fdf13fa24fa8fe
Update Dialog Messages during Companion Update

Change-Id: Ida8c09dfe0c5006516ea07d5104f85ff937b004a
Merge branch 'master' of https://github.com/mit-cml/appinventor-sources