previously only missing items could have tags added, a new option in radarr/sonarr settings allows
the addition of tags to existing media, using the existing tags used in missing items. also extracts
and refactors tagging functions to remove duplication.
fix#248
Adds new "Coming Soon" collection type, with options for Monitored in Sonarr/Radarr or Trakt
Anticipated. If a media file doesn't exist (unreleased TV Shows and Movies), a placeholder file will
be added (trailer if available). Poster overlays are added depending on its availability and
monitored status. Options for number of days to look ahead and number of days to keep item in
collection after release date. After this period the poster is reset. The placeholder file is
removed when an actual file gets added by Sonarr/Radarr.
fix#115
