Restore Odd Egg Ticket event.

We need to be a little creative here, because we can fully restore it without the mobile connection.
Revert "Remove GS ball save file checks."

This reverts commit 63307e2f58aab7b1ac042d65d7b1ae5c04469990.
Restore receptionist welcome to the trade corner.
Set mobile registered event when odd egg has been received.

We will use this event in place of PokeCom Center activation checks that have been removed.
Replace all "special $00a0" checks with event checks.

This routine checked if the mobile was registered in the Japanese ROM, however it always returns false in the English one.
Battle tower reference in EcruteakPokeCenter1F makes more sense after beating the Kimono Girls
Battle tower references make more sense when the player has actually battled there.
Restore PokeCom center reference in Celadon city