Clean up gene information on locus pages

[gymreklab]

• Change "Gene mapping" to "Gene Information"
• Figure out what happens when a locus maps to multiple genes?
• If there is no gene, say "No information available"

[ciarareeve]

currently postponing due to necessary api changes.

• genefeatures
• get_genes_with_exons

Changes have been made but not pushed until more information on webstr-db