Improve genetic variant information

[matthiaskoenig]

The additional meta-data on genetic variants is very limited. A detailed encoding of genetic variants is required which we then reference when encoding genetic variants of genes. Pharmvar just lunched their REST API. This finally allows to easily integrate with the information on genetic variants (https://www.pharmvar.org/documentation) and use a common nomenclature. See for instance https://www.pharmvar.org/gene/CYP2D6

• [ ] store additional information for genetic variants (gene sequences, identifiers, mapping on reference sequences)
• [ ] populate info nodes from pharmvar
• [ ] consistent nomenclature
• [ ] consistent info_node tree to filter on variants and variant information

See also #102.

[matthiaskoenig]

Additional information is available from the https://cpicpgx.org/ consortium.

• [ ] Gene-drug relationships with evidence https://cpicpgx.org/genes-drugs/
• [ ] allele definition and frequency tables