Added support to enter bootloader from software (bootloader version must be newer than "v2.18Jun 22 2018 17:28:08" until workaround for older is created).
Updated CTRL and ALT keymaps for entering bootloader with Fn+b held for >500ms.
Added basic MacOS keymap for ALT.
USB sleep LED indicator now turns off after 1 second.
Slowed down debug LED code printing.
