Disable the high current output and wait a little before to turn off,
because the interrupting capacity of the PSU is unknown.
Could be a function if needed by other.

From the prepare menu, accessible when is not printing, you have the
possibility to turn off the PSU when is on et vice versa.
From the host, you can turn off or turn on the PSU then the menu is
updated accordingly.
From the LCD message, the printer status is reported ready or off
respectively when the PSU is on or off.

Update Polish language 	#define MSG_RESUMING "Wznawiam drukowanie"

Fix to a bug that I just introduced - sorry. Forgot about offset of string length.

Add SD-Card change and SD-Card init. for reprap electronics without
SD-Chard change detect pin.

Use all available characters in narrow LCDs < 20 characters.

Fix to a minor bug with hardcoded LCD_WIDTH that draws edited values outside of the 16 characters width LCDs.

This reverts commit 01541ee64c.

[default off for now]
syntax: M600  X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]

if enabled, after a M600, the printer will retract by E, lift by Z, move to XY, retract even more filament.
Oh, and it will display "remove filament" and beep like crazy.

You are then supposed to insert a new filament (other color, e.g.) and click the display to continue.
After having the nozzle cleaned manually, aided by the disabled e-steppers.
After clicking, the printer will then go back the whole shebang, and continue printing with a fancy new color.

Add a feature to run the cooling fan at full speed for a small period
(default 100ms) when first starting the fan.  Some fans wont reliably
start spinning at low power, and many fans have issue with the PWM at
low power.  However, once the fan starts spinning it can reliably be
set to a wide range of PWM values.

Always set the FAN PWM value in check_axes_activity() and always use
the value of the active move if a move is active.