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.

engine/routines/townmap_convertlinebreakcharacters.asm

@@ -0,0 +1,21 @@
+TownMap_ConvertLineBreakCharacters: ; 1de2c5
+	ld hl, StringBuffer1
+.loop
+	ld a, [hl]
+	cp "@"
+	jr z, .end
+	cp "%"
+	jr z, .line_break
+	cp "¯"
+	jr z, .line_break
+	inc hl
+	jr .loop
+
+.line_break
+	ld [hl], "<LNBRK>"
+
+.end
+	ld de, StringBuffer1
+	hlcoord 9, 0
+	call PlaceString
+	ret