Firmware was forgetting the z_fade_height in Planner, set by M420 Z<f>,
after each reset or loading settings from EEPROM. Added the float
z_fade_height to EEPROM-Storage, now remembers the value.

==============================================

clarified BLTouch calculation & changed comment delimitters/flags

I found it hard to pickout the various sections in this area so I
changed most comments from // style to /** ... */

Made the BLTouch calculation simpler and clarified the units of measure
for the result.

============================================

add changes to example configurations

============================================

add TinyBoy2 to this PR & add BLTouch Delay

The OLED is driven by an SSD1306, connected to the board via
I2C, the rotary encoder is connected to 3 GPIO pins.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

- Add configuration support for zigzags in either the X or Y axis, for
wipe pads significantly longer in one dimension.
- Add configuration for default number of zig-zag triangles, vs. a
magic number in `Marlin_main.cpp`.
- Update description of auto nozzle wiping to match functionality

delay() is milliseconds

`Z_MIN_ENDSTOP_INVERTING` must match `Z_MIN_PROBE_ENDSTOP_INVERTING`
when using `Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN`.
This is easy to overlook.

- Fix typos, verbiage
- Fix naming of `setup_endstop_interrupts`
- Some formatting, indentation, spacing

If ENDSTOP_INTERRUPTS_FEATURE is enabled this tries to set up interrupt routines
for all used endstop pins. If this worked without errors, `endstops.update()` is called
only if one of the endstops changed its state.

The new interrupt routines do not really check the endstops and react upon them. All what they
do, is to set a flag if it makes sense to call the endstop test we are used to.

This can be used on:
* ARM (DUE) based boards - all pins can raise interrupts,
* RAMPS - all 6 endstop pins plus some other on EXT-2 can raise interrupts,
* RAMPS based boards - as long the designers did not change the pins for the endstops or at least left enough,
* all boards, if there are enough pins that can raise interrupts, and you are willing/able to swap with pins dedicated to other purpose.

・Update forgotten K8400\Dual-head\Configuration.h
・Adjust spacing

As pointed out by #5044