Add support for specifying return type of searches

Ability to map to different return type or to a JObject for raw results.

x.Search<U, V>(d => d.Index("logpipe-2013").Type("iis").Fields(u =>
u.Timestamp).MatchAll());
x.Search<U, JObject>(d => d.Index("logpipe-2013").Type("iis").Fields(u
=> u.Timestamp).MatchAll());
Merge pull request #217 from thelalle/raw-results

Add support for specifying return type of searches