Added:
- AMBrowseScansView ~ New class which encapsulates the shared elements
of AMScanDataView and AMChooseScanDialog. Essentially represents a
widget for displaying (with filtering capability) all the scans in the
database in the three major view modes (thumbnail, table, tree).

Altered:
- AMScanDataView and AMChooseScanDialog to now use an AMBrowseScansView,
instead of doing all that work themselves.
- AMScanThumbnailView - Fixed a few arithmetic errors that could occur
if functions were called in specific orders