Handle relative perceived effort (RPE) workouts

[bdlangton]

Here is a quick update to try and resolve the RPE issue that I raised here. You may have a better implementation but I'm hoping this is at least a starting point and helpful in illustrating what the problem I'm addressing is.

Previously, my RPE workouts would get copied to Intervals with no structure at all. With this update the structure is preserved, plus the RPE values end up showing up as text on the steps when transferred to Garmin:

- Warm up RPE 4-6 20m   

10x
- Hard RPE 8-9 1m   
- Easy RPE 2-7 2m   

- Cool Down RPE 1-4 15m