Change way votes are presented

Instead of displaying an 'Approvals' column listing each individual
vote, have three columns 'Test', 'Review' and 'Workflow' each showing
the lowest score. The 'Approvals' column is still available for those
who want to customize output column list.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Filter todo lists based on branch

Add --branch option to todo commands for filtering per branch

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reprioritize summary of votes

Instead of merely using numerical order to decide the most
important vote, ensure that we consider -2 and +2 higher
priority than -1 or +1.

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