Add TXL files to ARC

[davidkelk]

Adding txl files (who do mutation) to the arc repository.

[kevinjalbert]

If you could do the following that would be great:

• Add a python file that is able to:
  • Count the number of mutants generated per operator and return a dictionary of {Operator:value}
  • Clean up the generated mutations

[DONE] I will make to the config.py so that mutation operators can be enabled and disabled (also to specify their ordering). You just have to refer to the operators using the dict like config._MUTATIONS_ENABLE['CSO'] to get the value of the passed key.

[davidkelk]

Done and debugged.

[kevinjalbert]

I'll do a merge into the master branch then.