Currently:
- Civic-class structures have corresponding template_structure_civic*
- Economic-class structures have corresponding template_structure_economic*
- Military-class structures have corresponding template_structure_military*
- Resource-class structures have corresponding template_structure_resource*
- Special-class structures have corresponding template_structure_special*
However:
- Defensive-class structures have corresponding template_structure_defense*
This patch:
- moves *_defense* templates to *_defensive* for consistency
- updates all their specific children accordingly (did a grep)