Tested, merged and pushed. Thanks!

Pushed into branch issue205 in my repository.
Script is  src/search/unitcost and should be called with the preprocessor output 
file. 
It output either "unit" or "nonunit".

I'll take care of it

I think that we will need a script that detects unit-cost domains in a few
places (e.g. if we separately train unit-cost and non-unit-cost optimal
planners). Erez, I've assigned this to you in the hope that you could take care
of this, but if not, let me know and I'll do it.

Note that there are two different ways that a unit-cost problem could look like:

1) if use_metric is set to false (simple case)
2) if use_metric is set to true and the action costs for each action are equal to 1.