This commit checks whether or not HEATER_0 is in use, and if not, skips
the MIN / MAX temperature checks.

It wouldn't compile because of this line in temperature.cpp it turns out
it was just a stray ( that didn't line up with the previous lines so I
just made it in line with the rest and it compiled fine.

- Add comments documenting `thermal_runaway_protection`
- Add an enum for the thermal runaway states
- Add macros for temperature helper functions
- Fix a glitch with the z probe sled in homeaxis

and use them in temperuture.h

Flattened the if structure - the preprocessor is doing the work - not the Arduino. Arduino.

replaced GE0 with th matching GEX in the second row.
added some ()

- Make the default LCD click sound more pleasant
- Fix warnings about bed temperature runaway

cardreader.cpp needs temperature.h for autotempShutdown() when
AUTOTEMP is defined but warns about unused variables.
Unpublished variables by putting them in to temperature.cpp.

- Patched up for most included configurations

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

make it unconditional
remove all definitions in the 'Configuration.h's
remove form 'Conditionals.h'

to make the temperature-code work again with Arduino 1.0.6.

Sorry could not make an extra block on base level.

- Remove test of raw temp for thermistor 0 when using MAX6675
- Longer `raw_temp_value` array for `TEMP_SENSOR_1_AS_REDUNDANT`

- Get rid of unused temp states in the ISR, resulting in more frequent
temperature reading with fewer sensors
- Shrink code slightly in min/max testing

- Base tests on all thermistors/thermocouples, not just heater 0

- 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

- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS

- Make separate get_pid_output(e) and get_pid_output_bed() function
- Reduce size of manage_heater function
- Hopefully work around linker errors

- Fix for #1591 replacing #1595

This reverts commit fb75a9272d.

- Reduce calls to millis()
- General cleanup of manage_heaters
- General cleanup of pid autotune
- Formatting here & there
- Macros to clean up and shrink ISR code (reduced by ~364 lines)