Maintain annotation descriptions in a table

[david4096]

To make it easier to maintain new analysis values, and their descriptions, the metadata about each annotation could be made available in a database table.

Currently the page https://github.com/BD2KGenomics/brca-website/blob/master/content/help_research.md lists descriptions for each column name, with this change this page would be dynamically generated based on description records in a column description table.

We noticed this when generating GA4GH variant set records for the BRCA exchange variants. To provide metadata descriptions we will be hand copying values from this markdown document. @achave11