Refactoring form errors into separate methods

And testing the new form_is_valid function.
Adding a test for Form.form_errors()
Updating save_model_run

If the module provided is a python source file, it needs to be imported
via imp.load_source instead of through the python path as we normally
would.

Also adding an optional func_name argument.

Testing as well.
Consistent out_file naming and removal
Adding a method to save a form's data to python
Testing save_to_python
Adding parameter loading through the file menu
Allow get_file to save a parameter

Using a different dialog for opening an existing file or selecting a
new file.
Adding save parameters functionality
Saving file_dialog as local attribute per Form
Commenting out cached run menu option
Adding saving to python menu option
Disabling archivable json menu action for now
Commenting out Form's reset button for now