Currently artillery actors and Roman rams are located under art/actors/units/*/, but siege towers and other rams are located under art/actors/structures/*/, which is not only inconsistent, but also quite confusing.
- Moves the siege tower and ram actors to the units folder and updates all affected templates accordingly.
- While at it, also corrects the Greek specific names.
- Introduces a separate actor for the Kushite siege tower (the only difference is the garrison flag).
- Deletes the art/actors/structures/thebans/ folder, as it contains just one unused file, which is a duplicate of fireraiser already present in the units folder.