Started on changes AMScanDataView which will allow a popup
AMSortFilterWidget to control the proxy model for all child views.
Added:

- Support for lazy loading of thumbnails for scans from the database.
thumbnailFirstId and thumbnailCount are stored in AMLightweightScanInfo
(loaded by AMLightweightScanInfoCollection), and then when the
AMLightweightScanInfoModel requests them, the AMLightweightScanInfo
loads them from the database.

Altered:

- AMScanDataChildTableView now statically sets column sizes instead of
doing resizeColumnsToContents (which queries the whole model and thus
removes the benefits of lazy loading)