Make popup UI to customize pass/fail criteria for each lift type

[tlancon]

Currently you have to know the keys for set_stats and manually edit the JSON

[tlancon]

This needs to:

1. Read lifts.json into a dictionary
2. Allow the user to browse lifts in an intuitive, fail-safe way and edit the tags
3. Save the new tags to lifts.json
   • Do some checking to make sure the edited are valid
   • Or just design widgets that don't allow invalid input?
4. Reload the edited lifts.json back into self.lifts