Upgrade to use new evaluation engine

- Delete old naive and simplistic evaluation engine in favour of the one I have been developing for the past 4 months
- make evaluation non-sequential ie. if the user changes the code, the new code start evaluating right away, however, a new code evaluation thread will not cancel the thread executing the evaluation of the old code, that will probably be fixed in the futur
- update ace dependancy (it's no longer being hosted so added the javascipt file in our codebase)
- upgrade project to play 2.1.3
- unfortunatly, the evaluation engine dependency is added into the repo because I can't figure out how to do it using play/sbt