[annotation] Add LOFTEE and REVEL

[akotlar]

Background:

A concise description of why we're pursuing this task.

From Thomas:

I’ve not been following the sequencing literature that closely lately. I saw that the AD exome / WGS paper focused on some scores that I wasn’t very familiar with, REVEL and LOFTEE. I’m curious whether you think those are worth adding to bystro or about their utility, in general.

LOFTEE is fairly popular through its association with gnomad, so that one is worth including. Dave agrees. REVEL is worth evaluating, and including if easy (Dave suggestion)

Completion Criteria:

What is the goal, and how do we know this task is accomplished?

Update Bystro annotator to ingest/build REVEL and LOFTEE scores.

Implementation Summary

Give enough technical detail for a teammate to understand the proposed solution.

1. Investigate LOFTEE and REVEL output formats
2. Double check that our existing track format builders are flexible enough to support these
3. If not, add support
4. If so, build the tracks
5. Test
6. Deploy

This ticket will potentially need multiple PRs