template for connections page

instead of search #319, we can build a more accessible view of the /connections API which people can use to view onward connections from an object

closes #319

before build

[x] function to normalise URLs to their format in HC
[x] use URL normaliser to redirect to query string for normalised URL
[x] add form box so people don't have to mess with a query string
[ ] ~add link to Wikipedia page~
[x] allow empty query string (placeholder start page for now)
[x] add home button
[x] sort/split by source (V&A/SMG/Wikidata)
[x] add to bookmarklet
[x] write method to normalise v&a urls
[x] handle v&a objects not in the database (get their URLs and link to collections page)
[x] add a:visited selector to the CSS to make visited links purple
[x] add flag for V&A API pages