records: adds "Dataset" to record page & brief

* (addresses #514)
overlay: removes unused hmtl page
UI: updates "VM" pages for across site unification
UI: fixes "tabs" for all experiments
UI: fixes space between list items in "About" page

* (closes #594)
URL: experiment specific URL for visualise pages

* ‘visualise/events’ => ‘visualise/events/CMS’
* ‘visualise/histograms’ => ‘visualise/histograms/CMS’
* (closes #598)