Model Extension Definition Validation Should Report All Validation Messages And Not Stop When It Finds The First Error

The validation being done associated with MEDs is being done by the ModelExtensionDefinitionValidator. While the validator does perform validation in lots of different areas and reports issues in each of those areas, it does not report multiple issues within the same category. For instance, when the validator looks at all property definitions, it will only report the first error it finds in any of the property definitions. It should report all the problems from all the property definitions. Need to update ValidationStatus class so that it can contain multiple statuses and update the validator to report multiple statuses.