Create a variant list by selecting variants from gnomAD

[nawatts]

Add another option for creating a variant list. Given a gene, show all gnomAD variants for that gene. Allow selecting individual variants to include in a custom variant list.

The presented list of variants should include consequence, etc. and be filterable on some fields.

[nawatts]

This would require custom variant lists to have an option for an associated gene, so that the variant list includes consequences in that gene instead of the most severe overall consequence.