Updated all the example Configuration.h files for the new display type.

Minor wording correction.

- Make thermal protection for all hotends and/or bed into simple
switches
- Now enable `WATCH_TEMP_PERIOD` when `THERMAL_PROTECTION_HOTENDS` is
enabled
- Move detailed thermal parameters to `Configuration_adv.h`
- Add sanity checks to warn about old configurations
- Change `WATCH_TEMP_PERIOD` to seconds instead of milliseconds

in all Configurations.

- Add “Level Bed” menu item for auto bed leveling
- Hide the option if homing has not been done yet
- Arrange the Prepare submenu more logically (?)
- Add documentation comments, some white-space
- Apply some coding standards here and there
- Move old encoder multiplier debug option to `ultralcd.cpp`

K8200 example Configuration.h:
* STRING_URL removed: like proposed by thinkyhead in #1917

This addresses comments in #1956 and #1079. In particular, this is useful
when both endstops are stationary on a CoreXY system, and the Y axis needs
to be homed before the X so the flags are aligned.

With these changes the output of `M503 S0` is all you need to restore
the EEPROM. Building on this it is straightforward to save and restore
the EEPROM state using the SD card or external GCode file.

- Added `M145` to set “heatup states” for the LCD menu
- Added `M420` to toggle Mesh Bed Leveling
- Added `M421` to set a single Mesh coordinate
- Extended `Config_PrintSettings` with added M codes
- Cleaned up some comments here and there

Centralised beep code to lcd_buzz().
From gcode_M300() and lcd_quick_feedback().

Enforced max. duration for M300 to 5 seconds.

Corrected description in 'Configuration.h'

LCD_FEEDBACK_FREQUENCY_HZ 0 gives now a silent delay of
LCD_FEEDBACK_FREQUENCY_DURATION_MS.

Introduced in commit 697ee2dc and later spread to other files.

example_configurations\K8200\Configuration.h:
* merge upstream changes from default Configuration.h manually
* add some machine specific comments

Example Configuration for K8200 : comments/URL/readme

example_configurations\K8200\Configuration.h:
* add machine specific header
* change STRING_URL to K8200 fork (@thinkyhead: What do you think?)

example_configurations\K8200\readme.md:
* updated documentation
* added URLs and links

Example Configuration for K8200 : comments/URL/readme

example_configurations\K8200\Configuration.h:
* add machine specific header
* change STRING_URL to K8200 fork (@thinkyhead: What do you think?)

example_configurations\K8200\readme.md:
* updated documentation
* added URLs and links

example_configurations\K8200\Configuration.h:
* merge upstream changes from default Configuration.h manually
* add some machine specific comments

- Replace “Mendel” with “RepRap”

+ update in documentation

The line const bool Z_PROBE_ENDSTOP_INVERTING = false; // set to true to
invert the logic of the endstop is in the main configuration.h but
wasn't present in the example configuration.h's. Causes a compiling
error with Z Probe enabled. Just added it to all the configs. :)