Colourize approvals in tables

To make it easier to spot changes which are ready to be +A'd
or those which are already nacked, add colourization for all
commands.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Raise an exception if the gerrit command exits with non-zero status

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Allow rawquery passthrough for 'changes' command

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>