menu/bootscreen: do not init unused DMA registers
menu: add window data for a little loading message window
menu: use common list select function for main menu
menu: fade screen when no user interaction occurs (~10 minutes)
menu: begin adaptation to on-the-fly directory scanning
menu: new MCU command interface (FPGA block RAM @2a00-2aff), game loading handshake (WIP), NMI hook routine (WIP)
NMI hook contains meaningless code at the moment, mostly for testing. It is intended for in-game functions (WRAM cheats, controller query for IGR)
menu: reorder HDMA init, remove unused lenghty killdma function