* Refactor sorting and filtering compatibility code
Factor out parts of `TorrentFilter` and `TorrentSorter` classes into
reusable `FilterBase<>` and `SorterBase<>` templates.
Factor out filter and sort models setup from `FilterBar` and `Session`
classes into reusable `FilterListModel<>` and `SortListModel<>`
templates.
* Remove unused lambda capture (Clang build failure)
Mike Gelfand