Changed PE constructor to configure the pin modes as OUTPUT.
Removed from the Script destructor the cleaning of the next script. This will be moved to the Program destructor (probably a bad idea, though).
Added configurePins(..) to Program. Also implemented cleaning of the scripts in the Program destructor.
Changed executeSetProgram() to configure the pins after creating the program. Commented hack in setup()
Smalltalk commit:

* Renamed UziInterpreter to UziScriptInterpreter.
* Added UziSimulator, which will be able to execute several scripts.