Although its shape resembles a theatre, the gaul theatre is actually supposed to have a different function. This patch therefore renames it to assembly.xml. Now I'm aware an assembly is strictly speaking a group of people, not a building, but the same is true for e.g. congress, parliament, and senate; I doubt people will get confused by the new file name.
Furthermore:
- It changes the template's parent from template_structure_special_theater.xml to simply template_structure.xml, which means more duplicate lines now, but is cleaner, and makes future differentiation easier.
- It introduces an Assembly visible class.
- It adjusts the footprint, obstruction, rubble, icon, and sounds.
Meaningful values (e.g. cost, health, territory influence) are not changed; that should be done in a future patch.