Make setting to control pass/fail criteria of each exercise

[tlancon]

Lifter may want to monitor different aspects of each lift to determine whether it was good/bad or pass/fail

For example, I would like to indicate that a snatch fails if it's below a certain peak velocity, but I want to measure squats by the time of concentric motion

This needs to react to rep reassignment when #8 is implemented

[tlancon]

Moved pf_metric and pf_criterion to each lift's metadata in lifts.json. When the table and plots are updated, pass/fail is calculated using these parameters within an f-string passed to eval. This approach makes it easy to add/remove lifts and change their criteria in the json and have the app react to it.