Basic support for I2C display

* Based on Arduino LiquidCrystal_I2C library (need Wire and Twi libraries).
* Added functions setBufferOnly(), getLine(), resetBacklightTimer(), updateBacklight(), printSpacesToRestOfLine(), void print_P()
* Functions setBufferOnly(), getLine(), resetBacklightTimer() does not work, yet.
Readme updated
Code optimization. Wire library is not needed.

* IicLcd uses Twi instead of Wire.
* Removed unused API methods from IicLcd.
* Implemented getLine, printSpacesToRetsOfLine and resetBacklightTimer methods.
* Display turns off backlight after BACKLIGHT_AUTO_OFF_PERIOD seconds.
I2C bus speed set to 400kHz.
Merge branch 'feature/IICdisplay' into develop