MDriven Framework : we now require legal ocl in all oclColumns

Starting from 2018 and the support for VS2019 we made changes related to efficient load that make the framework check all oclColumns.

Prior to this point oclColumns could be ignored if no-one ever used them - but now - we assume that they are all used and thus valid. This is inline with our shift from placed handles to compound declarative ViewModels that are statically checked along with the model.

We will now throw exception if a n illegal ocl is found in the derivation phase.

If you would rather just log this with trace you can do so by setting the new variable:

/// <summary>
/// Set this property to false (default true) if you only want trace logging of failing derivations
/// </summary>
AbstractDeriver.ThrowExceptionOnFailedDerivation=false