* add command to display vanity callsign rules
* store callsign info in a separate file for extensibility
* Update callsign_info.py
* Update callsign_info.py
* fix gitignore, make pfx command extensible, fix US formatting
- Downsized multiple images
- Ran 'pngquant --quality 30-40' on all images
- MX bandplan had to be specially handled in Photoshop for both tasks
Part of changes for #38