Adds some generic meta tags to index.html to support link unfurling/twitter cards
Renames the SSR util composeHeadData to composeHeadTags, it now returns <title> and various <meta> tags needed for link unfurling/twitter cards, with the title and dataset for the selected dataset injected to the correct place.
metatags toindex.htmlto support link unfurling/twitter cardscomposeHeadDatatocomposeHeadTags, it now returns<title>and various<meta>tags needed for link unfurling/twitter cards, with the title and dataset for the selected dataset injected to the correct place.Closes #584