Change to VersionList property for base classes of revisioned entities

Revisioned entities in a PolicyPeriod have a VersionList property that contains a version list that is customized for the concrete revisioned entity type but adding a VersionList suffix. For example, for a Building entity instance, its VersionList property has the type BuildingVersionList. This property name and contents did not change, and none of that Gosu code is affected on upgrade.

However there were related changes:

• You might have written code that was general purpose such that it declared variables or function arguments as the base type EffDated or EffDatedBase. If so, there is a minor change if you accessed the VersionList property on either of those base classes. In version 9.0, the VersionList property on EffDated or EffDatedBase was renamed VersionListUntyped. Due to an unrelated change to base classes, during upgrade any use of EffDatedBase in your code must change to EffDated.
• On all concrete revisioned entity types (such as Building), from Gosu there is a new VersionListUntyped property. The value of VersionListUntyped is identical to the value of the VersionList property, but cast to the type EffDatedVersionList.