Supports both dual and single head printers (with the correct config).
Includes community sourced feed rate fix.

Rename / move files.

Remove redundant definitions.

Following up on #3231

The PrintrBoard Rev F utilizes a mcp4728 DAC to set motor current. Printrbot's implementation utilizes 2 new M-codes to set and write the DAC settings to the DAC EEPROM: `M909` (Read DAC) and `M910` (Write DAC). `M907` is re-used to set value, `M908` for direct control.

The Pins file for the RevF board is included.

Added support for BQ ZUM Mega 3D board and stock Hephestos 2 thermistor.

because of hardware differences on the SERVO0_PIN

Keep "astyled" reformatting

Currently we use the probe exclusively as a device to find the build platform(bed).
For the currently supported setups this means, we use it as a additional min-endstop.
A triggered when not deployed probe disturbs the homing process for max-endstops.

Rename ENDSTOPPULLUP_ZPROBE to ENDSTOPPULLUP_ZMIN_PROBE
Rename Z_PROBE_ENDSTOP_INVERTING to Z_MIN_PROBE_ENDSTOP_INVERTING
Rename Z_PROBE_ENDSTOP to Z_MIN_PROBE_ENDSTOP
Rename DISABLE_Z_PROBE_ENDSTOP to DISABLE_Z_MIN_PROBE_ENDSTOP
Rename Z_PROBE_REPEATABILITY_TEST to Z_MIN_PROBE_REPEATABILITY_TEST
Rename Z_PROBE_ENDSTOP to Z_MIN_PROBE_ENDSTOP
Adjust comments accordingly
Remove Z_MAX  check for the probe in update_endstops().

Using an delta related idea of @clefranc from #61,
extended to the general change for all setups.

Tested with Prusa i3, max-z-endstop and permanently triggered z-probe.
Worked for @clefranc's delta.

Apply `ENABLED` / `DISABLED` / `HAS_SERVOS` macros to pins files.

to MELZI_MAKR3D.

Fix for #2288
As the normal MELZI also can have a 1284.

- Add 3 new lines to `pins.h` to remove 2 redundant tests in
`pins_RAMPS_13.h`

No way to fit Marlin into 32K.

Copied from jcrocholl's contributions to the OpenBeamUSA Marlin fork

Created a new board to make using RAMPS as a CNC machine controller
easier. It maps pin 8 to the spindle and pin 9 to the controller fan.

is not used.

be.
Added Sanity Check for it.
Added hook so it's enabled.

Typo fixes in comments in existing code.

- Patched up for most included configurations

Z_DUAL_ENDSTOPS is a feature to enable the use of 2 endstops for both Z
steppers - Let's call them Z stepper and Z2 stepper.
That way the machine is capable to align the bed during home, since both
Z steppers are homed.
There is also an implementation of M666 (software endstops adjustment)
to this feature.
After Z homing, this adjustment is applied to just one of the steppers
in order to align the bed.
One just need to home the Z axis and measure the distance difference
between both Z axis and apply the math: Z adjust = Z - Z2.
If the Z stepper axis is closer to the bed, the measure Z > Z2 (yes, it
is.. think about it) and the Z adjust would be positive.
Play a little bit with small adjustments (0.5mm) and check the
behaviour.
The M119 (endstops report) will start reporting the Z2 Endstop as well.

- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS