Diffed and merged, preserving my updates

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%.

- 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.

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

Argument order of lcd_buzz was set to mirror that on tone(). Change
default M300 frequency to something audible.

Add new 'callback' edit-menu types that call a function after the edit is done. Use this to display and edit Ki and Kd correctly (removing the scaling first and reapplying it after). Also use it to reset maximum stepwise acceleration rates, after updating mm/s^2 rates via menus. (Previously, changes did nothing to affect planner unless saved back to EEPROM, and the machine reset).

Add calls to updatePID() so that PID loop uses updated values whether set by gcode (it already did this), or by restoring defaults, or loading from EEPROM (it didn't do those last two). Similarly, update the maximum step/s^2 accel rates when the mm/s^2 values are changed - whether by menu edits, restore defaults, or EEPROM read.

Refactor the acceleration rate update logic, and the PID scaling logic, into new functions that can be called from wherever, including the callbacks.

Add menu items to allow the z jerk and e jerk to be viewed/edited in the Control->Motion menu, as per xy jerk.

Conflicts:
	Marlin/language.h

This code selects between the routines for the GLCD or the char.
display.

A new variable was introduced to allow fan animation on the GLCD.
Add additional float to string conversion routine without sign
character. This is used for the coordinates visualisation on the GLCD.

This change also handles the case where the pause/stop/restart button on
the VIKI is not used. Make LCD I2C buzz sound the same as the normal
buzz (300ms is too long for quick feedback).

Refactor configuration to try to make items clearer (what defines a
panel vs what is user changeable).

This includes refactoring the buttons code to remove a large amount of
non-pin dependent duplication from pins.h.

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

[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.

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

This reverts commit cb02c2f9d8.

The number of steps per mm often contains 4 digits before the decimal point and does not require precision greater than 0.1

The joris' char drawins are expressed in binary so to show their content's in a more visual fashion.

This is not a code modification as much as a readibility modification.

The cli(); at the start of the kill() function also stops the internal
arduino timer which stops updating of millis() which prevents the
display of the "KILLED." message.
The new function updates the display directly without checking any
timers.

- related bug reports: Issue #201, Issue #213