ramps do have power for the servos, the power comes from the power connector, not sure why this note was even made

Changed "Bed Auto Level" (and variants) to "Auto Bed Compensation".

Added some background on the filament sensor to explain it better.

Added the new m-codes to this document.

sorry for that

Having actual section headers instead of just bold text makes those parts of the document individually linkable.

Not sure what happened to my last commit so this includes that one + reordering the steps.

Check the Readme for instruction how to enable and configure the feature

Dual x-carriage designs offer some substantial improvements for dual
extruder printing.

Untested

M109 S180 waits only when heating.
M109 R180 also waits when cooling.

Diffed and merged, preserving my updates

This change allows fan outputs to automatically turn on/off when the
associated nozzle temperature of an extruder is above/below a threshold
temperature.
Multiple extruders can be assigned to the same pin in which case the fan
will turn on when any selected extruder is above the threshold.
It also makes the M42 command compatible with the M106/M107 command.
The majority of the logic in this change will be evaluated by the
compiler at build time (i.e, low code space requirements).