Require sky map to launch a GRB RAVEN alert; fixes #517

This MR requires all GRBs to have sky maps before sending out an alert, a feature only required for coincidences involving Swift before. This means we will always wait for sky maps and the first publishing check will always fail to pass for GRBs. This will increase latency but at the benefit of significantly reducing the number of false alarms. Hopefully with the addition of !1101 (merged) the latency will be low enough to make it into the first preliminary alert.