Harmonising seqGWAS data

[ljwh2]

We need a better strategy to harmonise seqGWAS data, which sometimes perform well but sometimes suffer a high level of drop-outs, depending on the dataset.

Brainstorming doc is here: https://docs.google.com/document/d/1f40FNM2IEa0VW0RwKuZLsjO0GZ0rMU9JgRDuBYwftsk/edit?usp=sharing