Add support for arrayFilters in bsonkit.Apply

[amreo]

https://godoc.org/github.com/256dpi/lungo/mongokit#Apply https://docs.mongodb.com/manual/reference/method/db.collection.update/

I want to change the values of some items of a array. I think that Apply needs a another param.

[256dpi]

Array filters have not yet been implemented, hence the missing parameter to Apply. Once the implementation lands it will be added.

[256dpi]

Done!