Dedupe searches dropping limit

It is possible to pass a limit to dedupe screens in the url to prevent the entire database being searched for dupes. This can be important for stopping runaway queries crashing the site on large DBs. Recent code tidy ups caused this parameter to get missed in crucial places, causing queries to be missing this parameter. 

Although this is a recent regression it is to a largely hidden feature & I suspect we are the only users - hence setting to Major & not prioritising into the rc.