Add "eidolon-features" flag with every eidolon feature.

[MrVauxs]

This PR does the following:

• Changes the Eidolon Ability, Eidolon Symbiosis, and Eidolon Transcendence to gain features based on the flags.pf2e.eidolon-features.[initial | symbiosis | transcendence] flag
• Added an ActiveEffectLike to every eidolon ancestry to add UUIDs to the above flags
• Tagged the features in their descriptions
• Fixed #83
• Fixed #86 and #74

[!important] Existing Users will have to re-add the eidolon ancestry in order to gain the eidolon features at level 1, 7, and 17. Its best if they leveled down to 1 and back to player level, but its not necessary, since any already existing features will still be on the sheet after the change.

Ex.

{
  "key": "ActiveEffectLike",
  "mode": "override",
  "path": "flags.pf2e.eidolon-features",
  "value": {
    "initial": "Compendium.pf2e-animal-companions.AC-Features.WyN2qQ2AP4cOMNxF",
    "symbiosis": "Compendium.pf2e-animal-companions.AC-Features.6uCSkTAltByUK2Pb",
    "transcendence": "Compendium.pf2e-animal-companions.AC-Features.QDtXuIshSTUBcxff"
  }
}