Ported String types to Text

Changed all human-legible String types to Text. Also cleaned up some unnecessary type conversions and removed unused packages.
1. Prelude.map -- nooo! map should always be Prelude.map.
2. fmap is better to use than map, always.
3. This is can be defined much more succinctly in one small line. Have a look at Data.Bifunctor and think about what (fmap.fmap) f does.