Remove all code from main.asm (some labeled INCBINs, like out-of-context graphics, are still present)

engine/routines/ stores isolated out-of-context routines as individual files. It might be preferable later to append them to their related engine/ files in unique little SECTIONs, relying on the linkerscript to place them appropriately; or some other organization method. In the meantime, they're now easily findable apart from main.asm's other content.

constants/misc_constants.asm

@@ -93,6 +93,8 @@ NUM_HOF_TEAMS = 30
 ; significant money values
 START_MONEY EQU 3000
 MOM_MONEY   EQU 2300
+MAX_MONEY   EQU 999999
+MAX_COINS   EQU 9999
 
 
 ; ChangeHappiness arguments (see data/happiness_changes.asm)