* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Indeed the HAL does not need to be mucked around with to expose ATmega2560 pins not available as numbers on the MEGA board, I'll need to update the wiki with that tidbit and a reference to the pin-mapping comment in `fastio_1280.h`.

Co-Authored-By: Aaron Griffith <aargri@gmail.com>

* Allow both AD595 and AD8495 in concert
* General temperature code tweaks

This is an initial cut for feedback, updated for 2.0.x.

Chamber temperature is currently reported along with hot end and bed
temperatures to serial. The format is just like that used for hot end
and bed temperatures, but using 'C' prefix. As there is no heater,
target is always 0. Is this appropriate, is there a better way to report
chamber temperatures?

Chamber temperatures are not reported on the LCD in any way.

When auto chamber fan is enabled, it currently just uses the same
temperature threshold as the other auto controlled fans.

As the chamber temperature is not connected to any heater, it doesn't
undergo mintemp/maxtemp monitoring. This would need to change in the
future if chamber heating became a feature.

* Misc. Clean Up

Mostly UBL related clean up.
- But fixed a bug in the thermistortables.
- Made G26 more responsive to user aborts.
- Added sanity checks for older name for UBL_MESH_VALIDATION.
- Made G29 P4 able to edit invalidated mesh points
- Restore a reasonable Fade Height for UBL when creating new state information
- Get UBL's Topology Map to look a little bit better
- Make sure the user doesn't see a blank screen when doing Mesh Editing.

* Huh???   GitHub Desktop screwed up!

* get the planner object in scope

* Fix out of scope z_fade_height

* Travis timed out...

I need a change so I can force a new commit and sync.

Changes from #5485 by @AndKe

・Adjust spacing
・Standardize comments position
・Remove ',' at the tail of array

Following up on #3231

Thermister -> Thermistor

Added support for BQ ZUM Mega 3D board and stock Hephestos 2 thermistor.

//100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup) (calibrated for Makibox hot bed)

Caveat Emptor —- 
I’m not sure that this really makes sense,
but why keep someone from using it?

Keep "astyled" reformatting

Added a second sensor and made them configurable.

Am I the only one who always need to change the thermistortable.h to add
a dummy table??
Ok, it is done. Just set the thermistor to 999 and it will always read
25C. Great for Testing or Development purposes.