Improve output report

[nebfield]

Capture statistics in a consistent way from

• scorefile_read.py
• match_variants.py

And add them to the report

Include scorefiles that have been dropped for QC issues

[smlmbrt]

Variant Matching

• Summary of selected options (e.g. keep_amb keep_multiallelic)
• % matched (% of sum of variant weights missing)
• % ambiguous (if applicable)
• % fixed-strand flips
• Current bug: when multiple scores are present it uses the union of variants to calculate the percentages rather than a score-specific %)

Scores

• Mean, sd, key metadata (pgs_id, trait, publication?)
• Density plot (and splitting it by ancestry eventually)

[smlmbrt]

Mostly closed in #51

[smlmbrt]

Issue recorded in: PGScatalog/pgscatalog_utils#8