Update guide_gce.rst

Clarify which of the options to pick.
Update the GCE guide with a working configuration.

Also remove a few whitespaces, improve the bash script and fix a typo.
Merge pull request #9207 from rasputnik/patch-2

Update guide_gce.rst
Merge pull request #9209 from franckcuny/gce-doc

Update the GCE guide with a working configuration.
Creating initial framework for refactoring core codebase
Signatures
Some signature related things, prior to starting test scaffolding
Some restructuring.
Have a parallel development and test tree.
Make target for nosetests, no need to set library path for previous tests
Fix target in makefile
Move v2 out of the package tree so it does not yet appear.
Remove typo and intermediate dir.
Plan for unified CLI with subcommands?