bltouch: Add initial support for a bltouch "extras" module

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

test/klippy/bltouch.cfg

@@ -0,0 +1,73 @@
+# Test config for probe:z_virtual_endstop
+[stepper_x]
+step_pin: ar54
+dir_pin: ar55
+enable_pin: !ar38
+step_distance: .0125
+endstop_pin: ^ar3
+position_endstop: 0
+position_max: 200
+homing_speed: 50
+
+[stepper_y]
+step_pin: ar60
+dir_pin: !ar61
+enable_pin: !ar56
+step_distance: .0125
+endstop_pin: ^ar14
+position_endstop: 0
+position_max: 200
+homing_speed: 50
+
+[stepper_z]
+step_pin: ar46
+dir_pin: ar48
+enable_pin: !ar62
+step_distance: .0025
+endstop_pin: probe:z_virtual_endstop
+position_max: 200
+
+[extruder]
+step_pin: ar26
+dir_pin: ar28
+enable_pin: !ar24
+step_distance: .002
+nozzle_diameter: 0.400
+filament_diameter: 1.750
+heater_pin: ar10
+sensor_type: EPCOS 100K B57560G104F
+sensor_pin: analog13
+control: pid
+pid_Kp: 22.2
+pid_Ki: 1.08
+pid_Kd: 114
+min_temp: 0
+max_temp: 250
+
+[heater_bed]
+heater_pin: ar8
+sensor_type: EPCOS 100K B57560G104F
+sensor_pin: analog14
+control: watermark
+min_temp: 0
+max_temp: 130
+
+[bltouch]
+sensor_pin: ar30
+control_pin: ar32
+z_offset: 1.15
+
+[bed_mesh]
+min_point: 10,10
+max_point: 180,180
+
+[mcu]
+serial: /dev/ttyACM0
+pin_map: arduino
+
+[printer]
+kinematics: cartesian
+max_velocity: 300
+max_accel: 3000
+max_z_velocity: 5
+max_z_accel: 100