text: Title: Add a --version switch to the command line interface
  Body: ## Classification:
  
  Enhancement
  
  ## Summary
  
  Add a `-V` and `--version` command line switch that prints the current version.
  Use the `argparse` version action to implement it.
  
  ## Version
  
  AutoKey version: <=0.95.3
  
  Used GUI (Gtk, Qt, or both): both
  