Add query limits

[MER-C]

In XWikiLinksearch, searching certain domains (e.g. google.com) will lead to a timeout because the API cannot return the results in time. Another use case is where knowing that there are greater than X whatevers is enough, fetching the entire result set is wasteful.

A configurable hard limit (e.g. fetch the first 1000 results only) would be desirable.