first pass at overrides rewrite

overrides now live in default.cfg inside TAG.pak

skeleton/SYSTEM/rg35xx/paks/Emus/MD.pak/default.cfg

@@ -0,0 +1,14 @@
+-picodrive_sound_rate = 44100
+
+bind Up = UP
+bind Down = DOWN
+bind Left = LEFT
+bind Right = RIGHT
+bind Mode = SELECT
+bind Start = START
+bind A Button = Y
+bind B Button = X:B
+bind C Button = A
+bind X Button = B:L1
+bind Y Button = L1:X
+bind Z Button = R1