Add a gene symbol anchor to the result html page

[SimonLi5601]

This allows user navigate to the section with the gene symbol in the result page programmatically.

[oleraj]

Hi @julesjacobsen, we added this small change to our in-house copy of exomiser so we can create direct links to particular genes within the html file output. Any objections to merging this into master? That would allow us to use newer release versions without requiring us to remake the edit. I think it could be helpful for others as well. Let me know if you have any questions.