Infox box: Link for HGNC should reference "Approved Symbol"

[jvwong]

Description of new feature

Background: The search info box for a gene displays links to various biological databases, including HGNC. Currently the text and URI reference the 'HGNC ID' (format HGNC:XXXXX).

Issue: The goal is to update the link text and URI for HGNC to reference the HGNC approved symbol.

1. Text: "HGNC Symbol"
2. URI format: http://identifiers.org/hgnc.symbol/<HGNC approved symbol>

Motivation for new feature

This is in line with the format of biological identifiers kept in Pathway Commons.
@IgorRodchenkov

[jvwong]

My bad, the text for the link should not change - it should be "HGNC".