Rename the VRS Identifier the GA4GH VRS Identifier, reword help text

[melissacline]

• On the variant nomenclature tile, rename the VRS Identifier the GA4GH VRS Identifier

• Change the help text from "The VRS Identifier is a globally-unique identifier that removes a number of the ambiguities in variant representation" to "The Variant Reference Specification (VRS) is is a standard developed by the Global Alliance for Genomic Health (GA4GH) to facilitate and improve sharing of genetic information. The VRS Identifier is a computed string that identifies the variant uniquely and globally, with fewer ambiguities than other nomenclature systems".