Option to disable serial upload support for smaller boot section size

[per1234]

Check if this will save enough memory(removing the default network settings as proposed in #11 will also help).

• Use a define in the makefile to allow serial support to be disabled.
• The network configuration sketch needs to be uploaded via serial or ISP so this will need to be done before the non-serial version of Ariadne is burned and change the fuses in boards.txt to not overwrite the eeprom when the MCU is programmed by the bootloader.
  • It might still overwrite until the 2nd time the fuses are set(see http://www.freetronics.com.au/pages/how-to-upload-a-sketch-to-your-arduino-via-a-network).
• Custom tools menu for serial/no serial versions.