Improved support for panelolu2 encoder and buzzer

I added #define for LCD_FEEDBACK_FREQUENCY_HZ and
LCD_FEEDBACK_FREQUENCY_DURATION_MS  which is used to alter the default
buzzer sound.

When selecting Panelolu2 in configuration.h:
- it automatically sets the correct ENCODER_PULSES_PER_STEP and
ENCODER_STEPS_PER_MENU_ITEM.
- if LCD_USE_I2C_BUZZER is defined it will also set the default
LCD_FEEDBACK_FREQUENCY_HZ and LCD_FEEDBACK_FREQUENCY_DURATION_MS

When selecting the sanguinololu 1284p the following is true:
- its now enables  LARGE_FLASH
- It enables the gcode M300 when the panelolu2 LCD_USE_I2C_BUZZER is
defined
Changed 1284p fuse setting for Arduino_1.x.x

- Remove the two version of 16mHz. Crystal and resonator use the same
fuse setting. Also, Arduino IDE only showed the first one 16Mhz as a
board option.

- Added 20Mhz board option.

Symptoms for incorrect fuse setting:
- X axis move in one direction
- limit switches fail to trigger
- unable to reprogram the device via bootloader
- stops working when the reset switch is pressed.
- device fails to bootup when power by a slow raise power supply.

Solution:
- Disabled the jtag
- set the correct clock selection bit
- set the correct bootloader memory size
- enable brown-out setting
- enable clock power up delay
Merge pull request #743 from Opticalworm/Marlin_v1

Improved support for panelolu2 encoder and buzzer