Release a change log every data release

[jdhayhurst]

Every data release, publish a data change log containing a breakdown of new, removed, changed studies in the gwas catalog and summary statistics (submitted and harmonised). Previous changelogs should be accessible.

@sprintell We need to spec this up and figure out how it will be generated and where it will be published.

[ljwh2]

This was the intention of the "data release QC report" which was spec'd by myself, Daniel and Jackie (before I was project lead). I've tried to find out why this wasn't ever made publicly available but it seems the answer may be lost to history. It could be used as a starting point.