Final version of 3.0.6 firmware for Prusa i3 MK2

Summary:

Menu has been reorganized
Internal improvements of the menu system
Fixed a stack overflow
Improvements of the Live Adjust function (please rerun the First layer calibration)
Fixed the "Stop Print" function
Enabled a high power mode when first booted up on a brand new RAMBo board
Updated Spanish, Italian and Polish texts
Toshiba FlashAir SD card support is now switchable
"Calibrating nth point" message is shown during mesh bed levelling
New feature: Bed leveling adjustment
Improvements to fo fire safety
Improved unload filament function
Z-MIN set back to 0.15mm

The old Settings menu has been split to Settings and Calibration menus, where the Settings menu references the often used actions, while the Configuration menu references the rarely used actions.
"Calibrate Z" was redefined to let the user move the X axis up to the Z end stoppers and to re-calibrate the 9 bed point reference values after the printer has been shipped or re-seated.
New "Mesh Bed Leveling" menu item was added to the Calibration menu, doing what the "Calibrate Z" was doing before.

Use a shared menuData union for multiple menu screens to reduce memory allocation,
therefore reducing the risk of a stack overflow leading to crashes or an unexpected behavior.

Fixed a stack overflow leading to an unexpected behavior or a crash when moving a machine axis from the menu multiple times. This was a bug inherited from the original Marlin firmware.

Stepper driver timing was fixed in the baby step function. The original author of the Marlin firmware used a lengthy purposeless calculation to introduce a delay, but this sequence was recognized by the compiler as having no effect, therefore removed, leading to too short pulses, possibly having the effect of skipped steps in the Z axis during the Live Adjust.
Loading / reverting the Live Adjust offset after the 9 point bed leveling has been reworked to use the normal move planner instead of the questionable baby stepping routine.
Bugfix of the Live Adjust menu: Show the correct value instead of zero when the Live Adjust menu is entered.

Now the printer will maintain a valid coordinate system during the print stop, so it will not crash into the end stops when moving the print head to a rest position.

The langtool.pl was extended to understand annotations on the maximum text length and the maximum number of lines of mutli-line texts, which ensures, that the translated texts will be displayed completely.
The annotations were added to the English texts.
The threshold for hiding the Live Adjust menu was increased from 0.5mm to 2mm above the bed.

It is off by default. We had some feedback indicating, that some rare SD cards do not work properly with the FlashAir support.
The "Toshiba FlashAir" status display was improved to not force IP address query on each display refresh when in the "Support" menu and to update status of the Toshiba FlashAir on SD card insert / removal.

Message will now be shown on the display even if initiated from a SD card G-code.
The Z height will not be displayed on the status screen during the 9 point calibration, as this number is confusing, because it changes rapidly and it does not reflect the final Z height measured.

Adjustability at the left / right / front / rear side to fine tune the 1st layer squish.
The bed adjustment feature is accessible from the Calibration menu and as new L R F B codes of the G80 G-code.
The values are entered in micrometers, the maximum allowed correction is +-50 microns. In most cases this feature is not needed at all, but in rare cases when this feature is useful, we found that a correction in the order of 30 microns is enough to make the squish even.

Original Marlin FW and previous Prusa3D firmwares just stopped when printer detected risky behaviour. Now it stops the print, spins up both fans at 100% power and starts beeping. Both fans can keep hotend at safe temperatures even if the hotend mosfet would malfunction and was on 100% of the time.

Should keep less filament in the hotend and prevent some cases of jamming when loading new filament.