Adding correct member data gets messy

[chaban]

@Bitmap recently explained why this had to be done:

How to handle what seems like duplications

A while ago it was decided to split each instrument into its own relationship (but merge them for display in the UI). This was done to make data entry and storage more consistent; previously an editor could* set any number of instruments on a relationship, which meant that all of the following were allowed to exist simultaneously: original member: Ian McDonald (background vocals) original member: Ian McDonald (background vocals, flute) original member: Ian McDonald (flute) original member: …