Move Cnidarians to animals

[XylotrupesGideon]

the following icons:

anemone_release_of_acontia anemone_4-cell_stage_embryo anemone_adult_bleached anemone_gastrula_stage_embryo anemone_with_zooxanthellae anemone_asexsual_reproduction anemone_16-cell_stage_embryo anemone_adult anemone_blastula_stage_embryo anemone_planula anemone_eaten_by_Berghia_stephanieae anemone_polyp anemone_egg Hydra

are currently in plants/algae however, Cnidarians are animals. ther eis an argument to keep anemone_with_zooxanthellae in both categories as zooxanthellae are algae

[duerrsimon]

I have begun to work on a new backend where we can have multiple categories and tags. For now if you want to move them to animals feel free to do it by forking the repo and making the necessary changes.