Simplify asVersion()

By leveraging `get_object_vars($this)`, the static property arrays are no longer necessary.  The catch is that all exportable properties in child classes must not be `private`, or must be handled in a custom `_asVersion()` method.

When tests were added or modified, only minimal happy-paths were taken.  More robust testing is still needed for complete coverage.  The exception is `StatementTest` which had it's `testAsVersion()` updated to actually test functionality.  It's now the most robust test of `AsVersionTrait::asVersion()` in the whole suite.

I welcome your feedback and look forward to helping out and working with you on this and your other libraries.
In PHP is it possible to dynamically add properties to an object/class? Or is the class definition immutable? If it is immutable then this should be fine, but we want to avoid giving people a way to produce objects differently than is allowed through the interface in the object.