Better behaviour for Remove buttons

Right now, clicking Remove on say initial conditions, boundary conditions, etc, will remove the last item in the list.

This means that if we have say 10 items, and we want to remove the 5th one, then we need to hit Remove 6 times, and then _manually_ add back the 5 items we _didn't_ want to remove.

Instead, we should have a remove button ([bin icon](https://fontawesome.com/icons/classic/regular/trash-can)?) per item on the top right corner.