Names for general merge tactics in Data.Map

[David Feuer]

I realized that it would probably be helpful to put up the actual
documentation for the proposed functions. This can be found at

http://treeowl-containers-general-merge.bitballoon.com/data-map-lazy-merge

The almost-identical strict API (missing three fairly unimportant
contravariant mapping functions
that can't currently be made strict in an efficient manner) can be found at

http://treeowl-containers-general-merge.bitballoon.com/data-map-strict-merge

David Feuer