Ability to define our own search engines for paid search detection

[#1]

We're looking at using a relatively new search engine for some paid search work, and they are not listed in the drop-down box under "Search Engines" for paid search detection in the admin console. At the moment that means they'd be treated as a regular referrer and not included in the search engine reports, so we'd like the ability to add these guys to the list, just for our own reports.