• A Open action was added for the File menu, this action creates a QFileDialog with a filter for .py files.
• To manager the active document was created a DocumentController with a openDocument method and activeDocument property.
• A new class Document will load the data of the file.
• The UiController has a new method(setDocumentEditor) to set the Document in the Editor

You can open python files. If filter for python files will removed and you to open a different file, one QMessageBox will be opened.

Fixes T4551

Ref T1625