No WHERE push down support for = ANY and <> ALL

[Climax777]

Currently, there is no support for pushdown on WHERE clauses like = ANY or <> ALL, where Mongo's $in: [...] or $not: {$in: [...]} would work.

Although this is probably not the most crucial of features, I need it a lot for my use case, especially with arrays of ObjectIDs. This also needs #169, which is potentially fixed by #170 according to my specific testing.

A PR will follow shortly to address the array feature.