Global / Gene sample stats

Could do this by running code through sample stats but query is restricted to a gene instead of a sample. Then add onto that after annotation imports.

We could use gene sample stats to speed up for gene page variant grid is slow. If we could know the size of the grid, would remove a big database query. Visualise on gene page

Also keep track of global stats (maybe just add sample stats together) - interesting to know eg what % of our variants are in dbSNP or gnomAD etc, or intergenic etc. Could show some stats on variant page, and also VG front page