Add methods to Source::URL for determining whether a URL is an image
URL, a page URL, or a profile URL.
Also add more source URL tests and fix various URL parsing bugs.
Support grabbing the full image for Tinami uploads, rather than the sample.
Getting the full image requires making a request like this:
curl -X POST \
-H 'Referer: https://www.tinami.com/' \
-H 'Content-Type: application/x-www-form-urlencoded' \
-H 'Cookie: Tinami2SESSID=<redacted>;' \
--data-raw 'action_view_original=true&cont_id=1087268ðna_csrf=<redacted>' \
https://www.tinami.com/view/1087268
Then scraping the <img> tag from the resulting HTML page.
If the post has multiple images, then we need to scrape and pass the
`sub_id` of the image too.
Fixes#2818.
