Allow wider usage of ^ operator

[SSoelvsten]

Currently we only allow the ^ operator to be used directly on variables with a star-type. In most other cases it is not necessary, but one might as well allow a wider usage.

• Allow ^ on non-star type (treat is as a reference to whatever distance it has)

let eta1 : float[3] = Lap(1/3);
let eta2 : float[^eta1] = Lap(1/3);

• Allow ^ on expressions (infer the distance by the exp typing rules)

let eta3 : float[^(eta1 + eta2)] = Lap(1/3);

As before ^ should only be allowed within a distance, not within the expressions