Pace now supported in workouts

[Artur_Seres]

These threads also ask the same:

1. Build workouts using paces of fixed distances (eg. 1.2km @ 80% 5k pace)
2. Whether or not to support editing class schedules 5k, 10k, marathon pacing grammar
3. When editing a training session, can you set it by 5k race pace?
4. Specific Pace for Running Plan & Percentage Pace