Volume Tweaking...& "DIM"

At first, I programmed the minimum volume to be -63 dB. Mainly because I wanted to use a byte instead of an int and thus save precious memory space in the Atmel 168 (The DAC adjusts volume in 0.25 db increments, so 63x4=252 is the largest number a byte can hold). It turns out -63 dB is plenty loud with the DAC connected directly to the amplifier. So in this iteration:

• Increased control range from -99 dB to 0 dB
  
• Added a "DIM" control. This is like mute but it goes to -80 dB instead of total mute, and when you "undim", it goes back the the original volume. You can "undim with the same dim button and also with the volume control buttons
• The 4 buttons are now functional: right for "DIM", left for Filter, top for up volume and bottom for down volume. Sort of intuitive