gw/lts/skymap.py: add participating IFOs as tags
Add participating IFOs as tags to the sky localization metrics so that we can compare statistics for injections recovered by a single IFO to injections recovered by 2 or 3 IFOs.
Add participating IFOs as tags to the sky localization metrics so that we can compare statistics for injections recovered by a single IFO to injections recovered by 2 or 3 IFOs.