support --filter for restore

[Patricol]

Currently swww restore seems to use the default filter regardless of what had previously been set.

Feature request with two possible approaches:

Allow swww restore command to handle --filter flags. I imagine this is easier, but won't be ideal for people who don't use the same --filter flag for all outputs/imgs at once.

AND/OR

Have swww restore recall and use the --filter flag that had been set for each output/img.

I may be able to help with this, but I am very distracted by an OS switch, so it'd probably take quite a while to get around to.