Inconsistency in ROUND and TRUNC

[vpinna80]

The "behavior" section of round and trunc operators is inconsistent with the semantics.

They should be corrected as follows:

If numDigit is omitted or is set to 0, the operator has the behaviour of the “Operators changing the data type". Otherwise, for the invocations at Data Set level, the operator has the behaviour of the “Operators applicable on one Scalar Value or Data Set or Data Set Component”, while for the invocations at Component or Scalar level, the operator has the behaviour of the “Operators applicable on two Scalar Values or Data Sets or Data Set Components”, (see the section “Typical behaviours of the ML Operators”).

[amattioc]

I'll fix the docs. A wider discussion on this type of behaviour is open anyway (#409)