Enabled faceted searches are sorted randomly

In a workspace Faceted search configuration (Manage -> Locale Configuration -> Faceted search configuration), the selected value are bound to:

public Set<ContentViewHeader> getSelectedContentViewHeaders(
         ...
    }

This method returns a HashSet of which elements are sorted randomly. This is a problem since the order of the elements actually matters. Indeed, it will determine which Faceted search shall be activated by default on a given workspace.

We need to replace by Set by ordered list.