New general release

General release for all supported boards.

• Always connect endstops to X-MIN, Y-MIN and Z-MIN of the board, independant of endstop position
• Define homing direction with $23 (see https://github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#23---homing-dir-invert-mask)
• Laser PWM on Pin 2.5 (use minus pin of MOSFET connector)
• Default settings are for K40 chinese laser engraver
• $33 setting for PWM frequency (default 5000Hz)
• Set $5=0 if you have NO (normaly open) endstopps

Download your board specific firmware below to the SD card and rename it to firmware.bin!