Allow 2 filters on same field

[FelixMalfait]

I cannot add 2 filters on the same field such as "creation date > X" and "creation date < Y" ; or "name != x" and "name != y"

We should fix this. When you add a filter via the top right button it shouldn't automatically edit the existing filter for that field but instead it should add a new one.

cc @Bonapara