More SI474X family support and Examples with Automatic Volume Control (AVC)

Support to the advanced features of the SI474X devices
More examples and code optimization
This is an Arduino library for the SI47XX, BROADCAST AM/FM/SW RADIO RECEIVER IC family from Silicon Labs. This library is intended to provide an easier interface for controlling the SI47XX by using Arduino platform. Features:
FM (VHF) support (64–108 MHz);
AM (MW) band support (520–1710 kHz);
SW band support (2.3–26.1 MHz);
LW band support (153–279 kHz);
Allows firmware upgrade. Including the possibility of adjustments to demodulate SSB;
Advanced AM/FM seek tuning;
Automatic frequency control (AFC);
Automatic gain control (AGC);
Digital FM stereo decoder;
AM/FM/SW/LW digital tuning;
RDS/RBDS processor;
Digital audio out;
I²C and SPI interface;
More than 120 Si47XX function implemented;
Bluetooth Remote control examples;
EEPROM support (See examples)