194 - First test for maps

Create the C header for maps and fix up issues with bin export. Maps are the first thing exported, so that all offsets are positive relative to a given map. First test case: Use bullet_source_instances instead of enemy_instances for bullets schema. This is the first step in removing dependency on enemy data in bullets update, so hero and enemy will use the same bullet system. Todo: Update export_bt, remove enemy_instances_update dependency.