Generic tries (long)

[Jamie Brandon]

Ive put up the haddock api at http://code.haskell.org/gmap/api/GMap.html

The interface is now split into GMap which make no guarantees on
ordering and OrderedGMap which provides a compareKey function as well
as ordered folds etc.

> Because all maps ought to be traversable.

Thats a good point. Traversable requires Foldable. Do people expect
Foldable to imply some ordering? I can put it into OrderedGMap at
least.

Jamie