Fixed #26: Automatically Format on Save the First Time.
Extract getting python files from directory into separate method.
Parameter 'show_empty_panel' was removed.

The same info appears in the status bar.
Rename 'show_panel' to 'show_error_panel'.
Remove debug info.
Extract formatting source functionality into separate function.
Reformat code.
Use constants for timeouts. Remove unusage parameter from 'show_error_panel' function.
Hide output panel if there is no errors.
refactoring.