First step towards rich haskell environment
Add 'lens' to haskell

Because of its extensive dependency list 'lens' is a good test case
for the centralized haskell environment project.
Use profiled libraries
Haskell: simply the definitions; expand platform into packages
Haskell: add packages used in our projects
Some more Haskell packages
Merge branch 'haskell'

Provide some default Haskell packages.  Since this provides a new package
name for ghc and cabal, you have to do this after pulling:
  rm -rf ~/.ghc
  nix-env -e ghc-7.6.2-wrapper
  nix-env -e ghc-7.6.3-wrapper
  nix-env -e cabal-install