Unify LiftScreen field declaration API with type parameters

[indrajitr]

Some of field declaration methods have type parameters (like selectT, multiselectT ) and others don′t (like radio(...) ). It would be great all methods have type parameters for consistency. Also radio(...) is documented with “@param f a PairStringPromoter (a wrapper around a function) that converts T => display String” which is not used in the method declaration.

Discussion: https://groups.google.com/d/topic/liftweb/VbFjuuRPuv0/discussion

[github-importer]

Imported from Assembla: http://www.assembla.com/spaces/liftweb/tickets/1042