Update COLLECTION_LIST

[jekwatt]

Adds comments for clarification.

Updates COLLECTION_LIST with abbrev and Study/Cohort in report_merged_qc_results:

• 'TMCGVC', 'Causal Genetic Variants of Cardiomyopathy'
• 'TMGCUC', 'Genetic Causes of Unexplained Cardiomyopathies'
• 'TMREDS', 'Sickle Cell Disease REDS III'