added last of dap 'bits' to control_sgtl5000.* and include an example
for bass enhance, need to make one for surround stuff.

Added
AudioControlSGTL5000::dap_avc(..);
AudioControlSGTL5000::dap_avc_enable(..);

SGTL5000_Specific/dap_avc_agc example sketch

Also added 'public domain...' line to all my examples.