Add Panelolu2 support for Melzi

fix broken LCD commit #dfa549f268 from buildrob - GLCD/DOGM implementati...

LCD: Added Deadzone at 100% Feedrate

Implement automatic cold-end/extruder motor fan control based on nozzle temperature

Combine and converge other I2C LCD branches (PANELOLU2, VIKI & PCF8575)

This adds a deadzone at 100% Feedrate when changing it at the status
screen/main menu. Prevents from unwanted feedrate-changing when
navigating back to the main menu and makes it easier to return to 100%.

The I2C LCD status indicators now indicate when the hotends or bed are
turned on at all (rather than just when they are in their heating phase)

servosupport

BUGFIXES for temperature.cpp / add RUMBA thermocouple support

Fixed "Cooldown" Selection not reseting bed temp

- enquecommand with multiple lines "\n" doesn't work -> M140 S0 didn't
get processed. So I wrote a new func for the cooldown which uses
setTargetHotend. In addition this does return to status page after
selection.
    - Added setWatch() to preheat-functions (Temperatur sanity check
would never have worked when preheating from the lcd panel)

The Viki LCD rotary encoder uses a different number of steps per
rotation. This fixes the seeming "missed" steps when selecting a menu.

added support for the reprapworld keypad

- changed the variables from keypad to reprapworld_keypad
- added a missing ifdef check

BUG Fix in Commands M907,M350 and M351

The for loop for Axis count over the Array.
Add a break after M907

Solved minor bug in controllerFan()

Extruder 2 was checked where extruder 1 should be checked.

If S is left out perhaps it should be silent, but check the spec for
this M code.

Also cosmetic comment changes and spelling corrections in printed
messages

fix DEFAULT_AXIS_STEPS_PER_UNIT minor Z rounding error

(duplicates initialization in Marlin_main.cpp)

Also refactor extruder auto fan logic to simplify further and now only
check every 2.5 seconds