corexy: Initial corexy kinematic implementation

Add initial support for corexy kinematics.

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

config/example-corexy.cfg

@@ -0,0 +1,84 @@
+# This file serves as documentation for config parameters of corexy
+# style printers. One may copy and edit this file to configure a new
+# corexy printer. Only parameters unique to corexy printers are
+# described here - see the "example.cfg" file for description of
+# common config parameters.
+
+# DO NOT COPY THIS FILE WITHOUT CAREFULLY READING AND UPDATING IT
+# FIRST. Incorrectly configured parameters may cause damage.
+
+# The stepper_x section is used to describe the X axis as well as the
+# stepper controlling the X+Y movement
+[stepper_x]
+step_pin: ar54
+dir_pin: ar55
+enable_pin: !ar38
+step_distance: .01
+endstop_pin: ^ar2
+homing_speed: 50.0
+position_min: 0
+position_endstop: 0
+position_max: 200
+
+# The stepper_y section is used to describe the Y axis as well as the
+# stepper controlling the X-Y movement
+[stepper_y]
+step_pin: ar60
+dir_pin: ar61
+enable_pin: !ar56
+step_distance: .01
+endstop_pin: ^ar15
+homing_speed: 50.0
+position_min: 0
+position_endstop: 0
+position_max: 200
+
+[stepper_z]
+step_pin: ar46
+dir_pin: ar48
+enable_pin: !ar62
+step_distance: .01
+endstop_pin: ^ar19
+position_min: 0.1
+position_endstop: 0.5
+position_max: 200
+
+[extruder]
+step_pin: ar26
+dir_pin: ar28
+enable_pin: !ar24
+step_distance: .0022
+nozzle_diameter: 0.400
+filament_diameter: 1.750
+heater_pin: ar10
+sensor_type: ATC Semitec 104GT-2
+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
+
+[fan]
+pin: ar9
+
+[mcu]
+serial: /dev/ttyACM0
+pin_map: arduino
+
+[printer]
+kinematics: corexy
+#   This option must be "corexy" for corexy printers.
+max_velocity: 300
+max_accel: 3000
+max_z_velocity: 25
+max_z_accel: 30