Always call save_eeprom() when shutting down on purpose

We have "fallback logic" in the code to detect a supply voltage drop
and then quickly write the EEPROM values. The supply voltage is of course
gone when we switch off the FET...

If you connect too many peripherals to the 5V line,
the capacitor to drive the Arudino is emptied too fast
and the EEPROM values will not be saved.

This is a fix for shutdown via the menu,
the S-LCD and J-LCD displays.
Update display immediately on view change
Show total kilometers on boot up for 16x2 displays
New switch action: ACTION_FIXED_THROTTLE_VALUE

Sets a fixed throttle value via a long press of a switch.
The throttle value is reset once the switch is released.
Useful for triggering the starting aid, too.

The used power is configurable via the new
"fixed_throttle_in_watts" config.h entry.

Side note: The new action was almost called ACTION_TURBOBOOST_THROTTLE :)
Reset throttle_stat if SUPPORT_THROTTLE is disabled

This is needed to switch off ACTION_FIXED_THROTTLE_VALUE.

Don't do it for KINGMETER and BMS type displays though:
We can't ensure there is serial data to interpret on
every loop run, so we would make the starting aid act flaky.