Tools for adding external data about genes
Expand Gene model and add import function

The expanded data now expects each Gene to have several identifiers,
each unique to that Gene (hgnc_symbol, hgnc_id, ucsc_knowngene, and
ncbi_gene_id). Also renamed hgnc_name to hgnc_symbol to be more accurate.

Genes should be loaded by add_external_gene_data and new variants should
always refer to one of those existing genes.
Display Gene info on Variant detail