This moves the QSortFilterProxyModel to the resource model files,
acessible via a factory method, and moves the sorting and filtering to
the objects themselves, decoupling the code a bit.
This also adds a basic implementation of methods in the
ResourceFolderModel, simplifying the process of constructing a new model
from it.
Signed-off-by: flow <flowlnlnln@gmail.com>
1e2f0ab308