Startup core for MiSTer

• ESC - switch to options
• F1 - switch the backgound

Notes:

• Core supports sub-folders started with _ character.
• Regardless the place of RBF file, boot rom/vhd should be placed into either root of SD card or core's dedicated folder (should be created in root of SD card).
• Joystick (including emulation by keyboard) buttons defined in this core is default map for all cores unless defined in particalar core.
• In some cases when MiSTer is powered before TV/Monitor, there won't be a video on HDMI. Press the "USER" button or "RESET" to re-initialize the HDMI output.