* Fix up Travis CI and compile warnings/errors

* No ULTRA_LCD with REPRAP_DISCOUNT_SMART_CONTROLLER

* No point in setting all the endstop plugs

* Fix thermal protection documentation.

Even before the recent thermal protection changes, the documentation of
the thermal protection feature in the config files did not match the
implementation.  I fixed the documentation and reconciled the M303
implementation with the documentation.

* Applied documentation changes to sample config files

* Renamed hysteresis to watch_temp_increase

* Added gcodes back into documentation.

* Added M303 thermal runaway protection

Currently, thermal runaway protection is not available during M303.
Therefore, if someone plugs the thermistors in incorrectly and goes to
autotune their printer, the printer temperature could runaway and damage
could occur.

* Replace removed line, clarifying its logic

* Fixed M303 thermal protection

The temperature sanity checking logic was not being applied during M303
(pid autotuning) because instead of setting a target temperature, it
directly manipulated the pwm values.  When PIDTEMP/PIDTEMPBED is
enabled, PWM values rather than the target temperature determine whether
the heater is on.  I changed this to look directly at the PWM amount
when pid is enabled.

* Turn off heaters on M303 error

Currently, PID autotuning stops if it overshoots the temperature by 20C
or if if the temperature does not change for 20 minutes and it times
out.  I added calls to disable the heaters in these scenarios.

* Removed unnecessary if statement.

Added changes suggested by GMagician.

* Update temperature.cpp

* Update temperature.cpp

* Update temperature.cpp

Addressing #6992 and #5851

* Remove ADVANCED_PAUSE_FEATURE requirement for PROBING_HEATERS_OFF

* Add HEATER_IDLE_HANDLER conditional

Removing redundant_temperature from public section and leaving it in the
private section

* Unify M600 and M125 pause features
* Cleanup per thinkyhead's comments
* Rename filament_change_menu_response to advanced_pause_menu_response
* Include HAS_BED_PROBE in QUIET_PROBING
* Update gMax example file
* is_idle() is out of scope without the braces
* Convert FT-i3-2020 to Advance Pause names...
* Allow pause even if not printing

Saves a few lines of code.

 - rename to PROBING_HEATERS_OFF
 - move heater pausing functionality into thermalManager
   - add variables, pause(), ispaused(), other functions
 - add fan pausing functionality -> PROBING_FANS_OFF
 - add probing_pause() wrapper
 - move pausing into do_homing_move() and do_probe_move() to minimize quiet time and so other probe types can benefit
 - example configs

spi.h is only needed if HEATER_0_USES_MAX6675 is defined, so making its inclusion conditional on HEATER_0_USES_MAX6675 being defined.