Merging postreleasefix/84 to master
Merging postreleasefix/84 to master

* postreleasefix/84:
  [ENSWEB-2665] Track renderers can be changed via url

Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode