First pass at customizing for MakerGear M2.
Limit bedfan speed to half the full range.
Slow down default print move acceleration

This should help reduce banding due to oscillation.
Revert "Slow down default print move acceleration"

This reverts commit 3b509067d707e587c43a9dc5ff00f2a1695b3dd6.
Revert "Limit bedfan speed to half the full range."

This reverts commit 2557c6936bfb79dbf1b1dc65b3acd831f42a162e.
Add M108 to control MakerGear M2 secondary fans
Use automatic on/off for extruder/electronics fan

Instead of using M108 in gcode to control the fans, allow them to be
automatically controlled via extruder temp.
Revert "Add M108 to control MakerGear M2 secondary fans"

This reverts commit 6a523cdc3ea4857138018118e89022a516fde4c7.
Add support for VIKI LCD display and microSD card reader

changes made to get the VIKI display and SD card reader working
properly.  Added the needed LiquidTWI2 libraries.
DEFAULT_RETRACT_ACCELERATION  value

Return DEFAULT_RETRACT_ACCELERATION  value to the original value of
3000.
EXTRUDER_AUTO_FAN_TEMPERATURE value change

Change fan on/off value to 35C.  Extruder tends to bounce around 25C too
much during cool down causing fans to cycle on and off.
Add Custom Name

Define the CUSTOM_MENDEL_NAME as MakerGear M2 which will display in the
VIKI LCD.
Add M2 custom 50mm fan settings

Used to configure the firmware for the use of 12V or 24V 50mm bed fans.
Comment out #define M2_24v_50mm_Fan in Configuration.h to use a 12V 50mm
at ~12V.
Upstream Merge
Fix Merge Conflicts
Configure Firmware Retraction

Firmware retraction can now be enabled via the Retraction LCD menu.  It
can also be enabled by issuing a M209 S1 command.  To disable issue M209
S0.

I've corrected the LCD display issue and the feed rates are now in
mm/sec with a maximum value of 100 mm/sec.

For this feature to work you slicer must have retraction enabled and
some value for the amount of retraction.  When the firmware sees a
retraction event from the slicer the settings will be replaced with
those in the firmware.

On the fly changes to retraction can be made via the LCD.  The can also
be changed with gcode as below:

M207 - set retract length S[positive mm] F[feedrate mm/sec] Z[additional
zlift/hop]
M208 - set retract recover length S[positive mm surplus to the M207 S*]
F[feedrate mm/sec]
Add Firmware Retract to M503 output

Display current firmware retraction settings in M503 output
Streamline Firmware Retract to M503 output

Cleaned up crazy variables in favor of a casting the bool as an unsigned
long integer.