Add more information to embed HTML

Adds site link, license link and long name, replaces internal license name
(we don't have it for most licenses) with short name.

Also fixes some problems in previous changesets that I stumbled on,
renames things to be more consistent/less misleading, and makes
EmbedFileInfo a thin container for existing classes. (That results
in a lot of Demeter's law violations, but it means one less model
to remember, which is a good thing since our property names are
often not very informative (e.g. EmbedFileInfo.url and
Image.url which had completely different meanings))

We always have the site information for embed texts (comes from the repo
API); that part of the tests was pointless, but now that EmbedFileInfo
depends on Repo they became impossible to maintain, hence the
deletion of half the test cases in getThumbnailHtml().

Change-Id: I94e1d0aca14e2a7d5fad983412090add8ad6bfa3
Mingle:  https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/369
Merge "Add more information to embed HTML"