Adjust scaling of RGB GL waveform renderer to avoid clipping.
Move LibraryScanner and LibraryScannerDlg to src/library/scanner.
Restructure TrackDAO::getTrackFromDb to be a little more efficient.

* Remove duplicate calls to QSqlQuery::record (which copy the row).
* Remove O(n^2) algorithm for getting column indices.

Before:
Debug [Main]: Stat("TrackDAO::getTrackFromDB","count=50,sum=9.21243e+07ns,average=1.84249e+06ns,min=1.03929e+06ns,max=1.81965e+07ns,variance=6.67101e+12ns^2,stddev=2.58283e+06ns")

After:
Debug [Main]: Stat("TrackDAO::getTrackFromDB","count=33,sum=4.43607e+07ns,average=1.34426e+06ns,min=616956ns,max=8.00659e+06ns,variance=2.95187e+12ns^2,stddev=1.7181e+06ns")
Comment unused timer.
Switch default visual gain to 1.0.