[search] Support for extended query parsers

1. I think Extended Dismax should be the default query parser for Hue search with custom parameters (df,bf) for collections
2. At the very least, I should be able to append parameters to the query being sent to choose the "defType" for each collection

e.g.
defType=edismax&qf=features^20.0+text^0.3

Thanks
Prasanna