Fix MAGN-5376 Element.Geometry not working after reopening file.

<h4>Summary</h4>

I am regenerating the document before attempting to get geometries from elements. This will fix the defect. But because the test cases are running without starting a transaction, I am modifying the test framework to start a transaction in the setup method.

I added a new method OnEvaluationStarted which will be called at the beginning of an evaluation process. This method is overridden in RevitDynamoModel so that a new transaction can be started.

I am removing one call to ForceCloseTransaction in DocumentManager.Regenerate because it will be duplicated with the one call in RevitDynamoModel.OnEvaluationCompleted.

<h4>Reviewers</h4>
@lukechurch 
@pboyer 
This just seems odd, `DynamoRunner` shouldn't be invoking such a method on `DynamoModel.`  In fact, `OnEvaluationStarted` should be private, same with `OnEvaluationCompleted`.