Fix for #1460.

Seems to work with only one extruder. Can't test this myself with more.

A `z_before` value is passed to probe_pt, but the `retract_z_probe`
function assumes that Z is 0, doesn’t add `current_position[Z_AXIS]` as
other cases do. This may be superfluous, so this is a test, and will be
reverted if it has no effect.

- Fix `prepare_move` function not calling `adjust_delta`
- Add more shorthand for plan_buffer_line.
- Fix wrong `federate` usage, assuming they are all mm/m
- Minor `stepper.cpp` cleanup

- Users prefer `G29 E` to work like `M48 E` so fixed that
- `M48 n` replaced with `M48 P` (or `p`). `n` legacy support
- Shorten some strings to save precious bytes
- Smaller code for 3-point probing

- Fixed a typo causing G28 to home incorrectly
- Added documentation to G28
- Added homeXYZ bools to neaten the code
- Added a note about home_offsets being questionable

- Add some documentation to planner and stepper headers
- Patch up RAMBO pins with undefs
- Add `sync_plan_position` inline to set current XYZE
- Swap indices in `extruder_offset` to fix initialization values

- Patched up for most included configurations

- Also patch up some warnings

- Fix a bug reading `code_value` for `M503 Sn`
- Hide and remove unused variables

- Also a small tweak to SanityCheck.h

to avoid:
Marlin_main.cpp:1790: warning: array subscript is above array bounds.

- Init `zprobe_zoffset`
- Remove `current_position[Z_AXIS] = zprobe_zoffset` lines from the
`set_bed_level_equation_*` functions
- Apply standards to `mesh_bed_leveling` files
- Document `MESH_BED_LEVELING`

if not have SDSUPPORT the fromsd array is not necessary

It just probe all the bed without appliying the matrix.
Useful after a first G29 to check the topology.

ZigZag: Inverted Behavior.. If T supplied, it does not zigzag.
Topograph table: The table was rotated 90º clockwise.

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.

- Address issue #1669
- Remove the TOPO_ORIGIN configuration setting

- Address #1262 by leaving values as set
- Rename `add_homing` to `home_offset`

- Add `Conditionals.h` with calculated configuration values
- Add `SanityCheck.h` with checks for configuration errors
- Remove equivalent code from all configurations
- Move error checks from some sources to `SanityCheck.h` also
- Fix initialization of count_direction in stepper.cpp

Saves one addition.
Needs one pointer on the stack.

Don't know if this is a go trade.

Shoot in the dark.

Got:
Marlin_main.cpp:2567: warning: unused variable 'codepos'

Needs revision.
Don't now how this should look like.

Got:
Marlin_main.cpp:1689: warning: 'codenum' may be used uninitialized in this function

And indeed codenum is undefined when no parameter is given.

got:
Marlin_main.cpp:387: warning: 'delta' defined but not used

Compiles cleaner when definition is removed.

Users hat to press kill-button for unexpexted lon times.
See #1593

- Addressing issue #1608

- Add support for 4th extruder
- Fix parentheses matching
- Apply coding standards
- Address issue mentioned at #1575