merged from code downloaded from reprapworld.com

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

The new version of the library means that PANELOLU no longer needs to be
defined in LiquidTWI.h (the library file can be used as is) and the new
version of the library also enables the buzzer on the Panucatt VIKI
panel.

This allows PID_FUNCTIONAL_RANGE to use a maximum duty cycle higher
than PID_MAX. This is useful for powerful heaters to heat quickly in
bang-bang mode, but use a lower duty cycle that is easier to stabilize
in PID mode.

Definition for the graphic LCD are already in it, they will not harm the
configuration as they are only defined constants

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).

Definition for the graphic LCD are already in it, they will not harm the
configuration as they are only defined constants

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

Also fix compile time check in Marlin.pde

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

Removed incorrect LiquidCrystal_I2C Library

The extruder offset can be specified in the configuration
file or adjusted on the fly using the "M218 T# X# Y#" command.
The EEPROM support is not yet merged in.
The "T#" command can take option "F#" that specifies the feedrate
at which the printing head should be re-positioned. If not
specified the re-positioning move is not preformed immediately,
but the coordinates are adjusted for the printer to properly
position the head when the next movement happens.

This change makes the choice of serial port configurable so that
wireless capability can be easily added by connecting Bluetooth modules
(such as BlueSmirf or JY-MCU) to the expansion port pins.