Draft: pt-application: Add run once mode

• run-once mode

• run-once mode that checks for the existence of a "run-once" file in user config directory.
• If the file exists, the Phosh Tour skips launching, assuming the tour has already been completed.
• If the file is not present, the application launches as usual and creates the "run-once" file upon completion

• Autostart file for run-once mode

Fixes: #3