Google Cloud Platform updates

Please review and integrate this changes into the main autoparts repository. The new versions from the Cloud SDK and Google AppEngine SDKs are available, and the current autoparts version are no longer installable.

Side question: is it possible to host those files as Nitrous.IO pre-built packages? The issue I see is that when the sources are no longer available, particulary for the Google Cloud SDK, the instalation of the outdated package in a new box fails with an invalid checksum error.