Include #2892 to fix the isHeating symbol in the extruder graphics

Renamed `WARN_REDUCED_ACCURACY` to `DISABLE_REDUCED_ACCURACY_WARNING`

Changed the condition for blinking from
```
#if ENABLED(WARN_REDUCED_ACCURACY)
```
to
```
#if DISABLED(DISABLE_REDUCED_ACCURACY_WARNING)
```

Replaced displaying "---" instead of the value of a coordinate when
unhomed or with reduced precision
with blinking the coordinate-prefix-character ('X','Y','Z').
For "unhomed" a '?' is shown every second second - until that axis is
homed. The value displayed is, as before the "---" where displayed, the
relative to the reset position coordinate value.
When the axis stepper was disabled, now we can display a hint on that,
by showing a blinking ' ' instead of the axis letter, when
WARN_REDUCED_ACCURACY is defined.

I suppose the code itself is here the better documentation.

A '+/-' character is in non of our charsets so i decided for a '?' for
now to reduce the work.
There is no additional space on the displays one could use to display
the information, so replacing something is the only option. As the axis
letters are totally redundant with their positions on the display they
contain the least information.
So my decision was to overwrite them.

Introduce additional variable axis_homed to replace axix_known_position
when the coordinate display should indicate the axis is not homed.
This is to distinguish between "not homed" and "inexact position possible
because stepper was disabled".

# Conflicts:
#	Marlin/ultralcd_implementation_hitachi_HD44780.h
solved

Implement and test blinking for char-lcds

# Conflicts:
#	Marlin/ultralcd_implementation_hitachi_HD44780.h
solved

Keep "astyled" reformatting

Saves about 473 byte of progmem and 28 bytes of RAM.

Apply `ENABLED` / `DISABLED` macros to LCD-related files.

The volumetric multiplier display needs to be multiplied by 100 in order to make it an integer for display purposes.

Moved SDCARDDETECTINVERTED and SDSLOW to Conditionals.h.
Added U8GLIB_LM6059_AF to define display specific actions.
Added reminder to compile in u8glib

Rename of define to avoid confusion between the controller and the
display which had similar names.

Fixes for some code formatting changes and commenting out the
ADAFRUIT_ST7565 define that was left defined.

Added support for new display type

- Also show 2 digits past decimal for Z on DOGM

- 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`

Edited the European part of 'ISO10646_CN.fon' to match the existing fonts.
Added Chinese font to make_fonts.bat
Created 'dogm_font_data_ISO10646_CN.h'
Added Chinese to 'language.h'
Added 'language_cn.h' with some minor edits.
Added Chinese font in 'language_en.h' to not fall back to European font.
Added cn to 'Configuration.h'
Changed WIDTH to LCD_PIXEL_WIDTH and HEIGHT to LCD_PIXEL_HEIGHT to have more descriptive names.

In 'dogm_lcd_implementation.h'
Added Chinese Font
Made 1 pixel more room for the larger Chinese font on the status line.
Changed geometry of the 'select bar' by one pixel.
Changed the way the position for values and postcars are set.

to avoid errors in Marlin_main.cpp. #1860

In the include tree of Marlin_main.cpp the decision between the display types is not made.
To include the right LCD_STR_* ether 'dogm_lcd_implementation.h' or 'ultralcd_implementation_hitachi_HD44780.h' with all their code.
A 'dogm_lcd_implementation.h.h' would be a curiosity.
So i moved both of the definition blocks to conditionals.h

On the long term it could make sense to use the same numbering for the u8glib and the hitachi symbols.

Just and only display splashscreen only once.

This reverts commit bf04a92cc0.

Example for splash screen.

Splash screen was shown with every display init.
That means every time the menus where entered.

Note the 2 in the initialisation.
The buffer is already written in two steps a 512 byte.
Without the 2 only the upper half is shown.

In 'if (encoderPastThreshold || LCD_CLICKED)' lcdDrawUpdate was not set.

'lcd_status_update_delay'-loop was not effective in  function
lcd_status_screen().
The loop prevented the update of the status screen but not the displays
update.
Shifted the loop into lcd_update().

This reverts commit 6361404b91.

Shifted condition should still be in.

Result see: https://www.youtube.com/watch?v=tdu7J0i-c4g
Loop is executed several times per display update.

This rolls back to commit 06f767d608.

Thanks @MagoKimbra.

Fix for #1460.

Seems to work with only one extruder. Can't test this myself with more.

and satisfy the compiler about the implicit compare.

to avoid warnings about unused blink.

Concentrate definitions of variables in dogm_lcd_implementation.h to one place.

Make only local used variable currentfont static.

Tweak the documentation