Add an additional (optional) operator to the search fields to signal the fields should be searched for in AND or OR operators when searched for the same fields.

Example:

   search[value][]=Titel:=:OR:Fedora
   search[value][]=Title:=:OR:Ubuntu

searches for either Fedora or Ubuntu in the same query. This also reverts the change where for the title field, always an OR was performed (so searching for two titles, would result in a search for either instead of for both).