Unify FlowHideLayout and FlowWrapLayout #168

The idea of these layout managers is to do something when the available space in the parent becomes subjectively too small.

Flow hide layout manger

If the space becomes too small, it will hide some columns. This is for the cases where wrapping elements into different rows/columns is not an option. Like in the backlog where it would look awful when the buttons are all over the place.

Flow wrap layout manager

If the space becomes too small, it will wrap the last components to a new row.

The issue is that both layouts share the same trigger, but perform different actions. It would be sensible to introduce a shared parent class or use composition to delegate the trigger onto a shared piece of code. This way improvements to one layout, will carry over to the other.