Various improvements

* Drop support for cabal-dev

* Allow .cabal-sandbox to be in any directory of the dir hierarchy (not
  just current dir)

* Perform .cabal-sandbox lookup once at the beginning, not on every file
  change

* Remove warnings from the code
Update testloop-example to adapt to latest changes of testloop
Add a .ghci file for the project
Strict fsnotify to 0.0.8, other versions don't work correctly :-(