REPL mode when started without command line parameters

[coldfix]

Might be nice in certain situations. Though, this requires a minor language redesign: inquiries can only be posted after the constraints are added, and there should be special syntax to distinguish them. I'm thinking of something like:

./Citip
> X/Y/Z
> check I(X:Y:Z) <= 0
...

On the command line use something like --inquire or --check (+short form). I don't think constraints should be required to be marked as such, but for explicity, one could add for example a --constraint option (although the short option is in conflict with the one of --check).