[Meta Workflow] Only create new WorkflowMetaTypeVersion based on latest versions

[JoaoRoxoNeves]

In the management back-end interface to edit the WorkflowMetaType, remove from all the old WorkflowMetaTypeVersions the button to create a new version.
Only the latest WorkflowMetaTypeVersion can be used to create a new version.

Also remove all the domain code to support this funcionality; reduce and simplify the remaining code.