Bug 1210846 Auto Reset Gain & Eq after each song

-Added a checkbox under preferences->equalizers for enabling Auto EQ/Gain
Reset
-If checked, resets the pregain, lowgain, midgain & highgain to defaults when a new
song is loaded
Correcting for PR comments
getValueString: using the overload providing a default
Merge pull request #365 from raulbehl/master

Bug 1210846 Auto Reset Gain & Eq after each song