Moved the DataType ID constants to the uComponents.Core project.
Added a stub class for the PropertyEditor alias constants.

Wrapped the DataType ID constants in the `Constants` static class/helper.
Re-added the `DataTypeGuids` constants class.

As I broke backwards-compatibility.
Updated the DataType GUIDs with the new references.
Created the mapping for the legacy DataType GUIDs with the new PropertyEditor aliases.
Added a few stub aliases for known PropertyEditors in development.