Node::toString Link::toString do not print TV appropriately and break test units when modified

[Nil]

Node::toString and Link::toString rely on TruthValue::getMean() and TruthValue::getCount to generate the string of the atom's TV. As a consequence it misses VersionedTVs when the TV is CompositeTV.

This can be easily fixed by relying on TruthValue::toString but when trying to modify Node::toString and Link::toString adequatly then more than a dozen of test units failed. This clearly is indicating a problem in the test units or worth in the code.

[Nil (ngeiswei)]

That was just an oversight, if extended correctly Node::toString and Link::toString do not break the test units.