Add RIR/RPE per set

Please make it possible to enter reps in reserve (RIR) and/or rate of perceived exertion (RPE) for each set since many programmes call for working from 3RIR in the beginning of the cycle to 0RIR at the end of the cycle. Being able to track this would allow to increase reps not just measured by numbers in comparison to last week, but also in regards to RIR from last week.