Check reading of old data and add unit tests for each file version

Reported by Mark Telling (ISIS) on July 30th 2019, who could not reanalyse old IN16 elastic scans. Checking the problem I found that at some point I had messed up in rdid.pro, so this case (elastic scan with the PSD detector) was not handled correctly. It seems this has been there for a long time (probably since 2014), but apparently not discovered before (or not reported). I am going to implement a quick solution for Mark's case, but ideally, reading of all old data should be checked and introduced as unit tests. I will try to start with IN16 and Salsa, and then continue with other instruments.