Organize the engine/ directory

This is an informed attempt at reorganizing the engine/ directory by
creating categorized subdirectories, in order to make it easier to
navigate and find things.

The directories created are as follows:
* engine/game: Contains all "minigames", things like the unown puzzle
and slot machine.
* engine/gfx: Contains all handling of graphics. From loading palettes
to playing animations.
* engine/link: Contains all multiplayer functionality.
* engine/menu: Contains all generic/misc. menus and menu code.
Other, more specialized menus are in their own subdirectories (pokedex,
pokegear, party menu, etc).
* engine/overworld: Contains all handling of the overworld. From loading
and connecting maps to wild encounters and the scripting engine.
* engine/pokegear: In the same vein as engine/pokedex, except it could
use some more splitting up.
* engine/pokemon: Contains everything related to manipulating pokemon
data. From the pokemon storage system to evolution and mail.
* engine/printer: Contains everything related to printing things as well
as the printer communication.
* engine/title: Contains intro sequences, title screens and credits.

engine/link/time_capsule_2.asm

@@ -0,0 +1,39 @@
+ConvertMon_2to1: ; fb8f1
+; Takes the Gen-2 Pokemon number stored in wd265, finds it in the Pokered_MonIndices table, and returns its index in wd265.
+	push bc
+	push hl
+	ld a, [wd265]
+	ld b, a
+	ld c, 0
+	ld hl, Pokered_MonIndices
+.loop
+	inc c
+	ld a, [hli]
+	cp b
+	jr nz, .loop
+	ld a, c
+	ld [wd265], a
+	pop hl
+	pop bc
+	ret
+; fb908
+
+ConvertMon_1to2: ; fb908
+; Takes the Gen-1 Pokemon number stored in wd265 and returns the corresponding value from Pokered_MonIndices in wd265.
+	push bc
+	push hl
+	ld a, [wd265]
+	dec a
+	ld hl, Pokered_MonIndices
+	ld b, 0
+	ld c, a
+	add hl, bc
+	ld a, [hl]
+	ld [wd265], a
+	pop hl
+	pop bc
+	ret
+; fb91c
+
+
+INCLUDE "data/pokemon/gen1_order.asm"