Rewrite all setup scripts using clean bash conventions and &&-chains.
Rewrite SetupGerrit to provide more information, instructions, and links
to the user.  Also teach SetupGerrit to configure a http fetch url and
ssh push url so that "git gerrit-push" does not need to access the SSH
private key twice.

Change-Id: I60d790cc23ff6296dee54d789ed492beb74a369c