Wrangle data from redcap into more usable formats (long & wide)

Started to document the [redcap wrangling code](https://github.com/KirstieJane/NSPN_Longitudinal/tree/master/BEHAV_DATA/PROCESSING_REDCAP) in [NSPN_Longitudinal](https://github.com/KirstieJane/NSPN_Longitudinal/) repository as a [wiki page](https://github.com/KirstieJane/NSPN_Longitudinal/wiki/Processing-Behavioural-Data-from-RedCap).
