Collapsible advanced filters

[lemeryfertitta]

As discussed in #39, we can free up some space on the filters page by having an "advanced filters" collapse.

For now, I'd like to move Min Rating and Grade Accuracy to this new collapse. Another future candidate for this would be a Setter search. This would be a pretty easy add, so we can tack that one onto this issue as well.

[gardaholm]

Something like this? Tried some toggles or indicators, but somehow the label got either to big (with expand / close icon) or the button/label got too prominent. I would go for the cleaner solution and don't make this label too big or prominent.

[lemeryfertitta]

Deployed