Create LTL.__repr__
Create LTL.__repr__

Thus, in accord with the standard meaning of __repr__,

    from tulip.spec.form import LTL
    f = LTL('[](a -> <>b)',
            input_variables={'a': 'boolean'},
            output_variables={'b': 'boolean'})
    g = eval(repr(f))

will result in two LTL instances, f and g, that are distinct objects
(in terms of pointers and memory allocation) but have the same value.

necozay/tulip-control,tulip-control/tulip-control,necozay/tulip-control,tulip-control/tulip-control,necozay/tulip-control,necozay/tulip-control,tulip-control/tulip-control,necozay/tulip-control,tulip-control/tulip-control