Resource IDs and scene/har IDs need to be separated.

[katajakasa]

We've been using resource file id's for pointing at HARs and Scenes. So far this has been fine, but now we're making scenes that load other scene files. Eg. SCENE_SCOREBOARD loads SCENE_MENU file. So, we might want to separate resource file ID's from the scene and HAR id's. TODO:

• Rename all HAR* to AF* in ids.[h|c]
• Rename all SCENE* to BK* in ids.[h|c]
• Add SCENE_* names to common_defines.h
• USE SCENE_* names for pointing out scenes to load, and use resource id's for telling the loaders what resources to load.
• To help in this, we might want to add har_id_to_resource() and scene_id_to_resource()
• Rename HARNAME* in commondefines.h to HAR*
• Rename PILOTNAME* in commondefines.h to PILOT*

[katajakasa]

Done @ c8143bd0d5e90ed73771b32c6337bc74380153ab .