DMN16 — Rounding functions introduced in DMN 1.4 should have single parameter version

Currently the 4 rounding methods: round up, round down, round half up, round half down only have signatures with 2 numeric arguments (n and scale).

However, pre-existing rounding functions: floor and ceiling have both a single numeric argument version and a 2 numeric argument function (n and scale).

The single numeric argument is backward compatible with DMN 1.3 (and before). It assumes a scale of 0.