DMN11 — Remove attribute DecisionTable/@isConsistent

I think this attribute is inappropriate. It reflects a model validation condition, not a design-time property. Moreover, it has default value "false", suggesting that any model that omits this attribute is intentionally inconsistent, which makes no sense to me.

This is a bit different from isComplete, where false could possibly be intentional at design time.

*Remove consistency info from model *

we could define the concept of consistency, so that tools will behave consistently, but it does not seem to belong in the model. Rules are either consistent or not, regardless of what some flag might say.