Add setup_cabal.sh: a script to set up cabal

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>
Add setup_haskell_sandboxes.rb script

This is used to install various Haskell packages that I use in Cabal
sandboxes. More documentation will be added later.

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>