Marlin v1 i2c lcd

Hi Erik, 
I've added support for  LCD displays controlled via I2C  (PCF8574 I2C portexpander). I've included the LiquidCrystal_I2C Lib (from http://hmario.home.xs4all.nl/arduino/LiquidCrystal_I2C/) for Arduino IDE > 1.0. A tutorial for working with PCF8574 can be found here: http://garagelab.com/profiles/blogs/tutorial-lcd-using-only-2-arduino-pins-with-pcf8574-and-i2c. 
Tested on GEN7 and Ramps 1.3 (MEGA 1280) so far.

best regards 

Christian