These are salvaged from closed-PR #3216.

Follow the PR #3242.

Closes #3245

Fixed backlight for PCF8575.

Signed-off-by: Christian Inci <chris.pcguy.inci@gmail.com>

In all these cases we want the axis to be homed. If we could have lost
some steps is secondary.

Reenables homing seperate axis with DISABLE_X / DISABLE_Y true.

copy of 406992f9dd

Also add mbl.z_offset to the EEPROM, bumping the version to V23.

Following up on #3231

PROBABLE ->PROBEABLE
This is follow-up to #3069?

Fixes for #3189

Setting a temp is still missing

Adds the parameter U to M303. If U1 is included , it will use the
PID-values from the auto-tune.

Send position updates to RH where RH can not know the end position.

For example after G28 RepetierHost assumes to be at the homing-point,
but with a servo probe we are much higher. Now the RH-software-endstops
will prevent us from going down (if activated). With this patch the
internal position of RH is updated with `current_position[]`.

Sorting ot what else belongs to what if was not so hard.
But the static `ms = ms = millis();` was a bit surpising.

Follow-up the PR #3082
Follow-up the commit 143ad74: unnoticed updates
Fix for commit b0f5ba0: Z offset: -front [of the nozzle] +behind -> Y offset: -front [of the nozzle] +behind
Standardize the writing method: Z-probe, z-probe -> Z Probe
Adjust spacing

documentation/LCDLanguageFont.md moved to http://www.marlinfirmware.org/ at commit 12d0983757,
but http://www.marlinfirmware.org/ isn't working.