[LIBCLOUD-611] Added ex_create_image for the GCE compute provider

[katrielt]

Resolves https://issues.apache.org/jira/browse/LIBCLOUD-611

[Kami]

Docstrings need to be updated.

[Kami]

@katrielt Can you please synchronize your branch with trunk and squash all the commits (I'm having problems merging this directly into trunk).

Also, next time feel free to ping me after you address the issues since I don't receive a notification when you push new commits.

[katrielt]

Thanks for the ping. Was un-aware of that.
I've attached the squashed and formatted patch to the jira case at https://issues.apache.org/jira/browse/LIBCLOUD-611

[Kami]

I still had some issues with applying the patch since it appears your branch is not synchronized with trunk, but I went ahead and picked the changes manually.

Changes are merged into trunk now - thanks.

[katrielt]

That is weird, as I pulled from the upstream repo. at https://git-wip-us.apache.org/repos/asf/libcloud.git. Anyway, thank you.