This patch is split off from D2953.
Several unused and useless fauna templates are deleted:
* `template_unit_fauna_breed.xml` and `template_unit_fauna_breed_passive.xml` only change the vision range;
*, `template_unit_fauna_hunt_passive.xml` and `template_unit_fauna_wild_passive.xml` only add a <DefaultStance>passive</DefaultStance> line; however, this is already inherited from `template_unit_fauna.xml`.
Having unused files is fine, provided they're useful. These fauna templates are unlikely to be ever used, therefore it's better to remove them.
Furthermore, `template_unit_fauna_herd.xml` has only one child: `*_domestic.xml`. Both contain only a few lines. This patch merges the two and adjusts the parent lines of domestic animals accordingly.