Fix bugs in Variants API RST markup
Fix bugs in Variants API RST markup

Images should now load, and cross-references to Avro records should
now be real links.

heuermh/ga4gh-schemas,pcingola/schemas,diekhans/ga4gh-schemas,ga4gh/schemas,macieksmuga/schemas,saupchurch/schemas,dcolligan/schemas,diekhans/ga4gh-schemas,ga4gh/ga4gh-schemas