Improve image copyright references on invasive portal

[mikkohei13]

Improve this image copyright notice so that

• Has proper padding & looks nice
• Doesn't show photographer name multiple times
• Shows full CC license name
• Creative commons license has link to the license deed page
  • e.g. Creative Commons Nimeä Jaa-Samoin 4.0
• Shows caption, if exists in the selected language. (This sometimes contains link to image source, which is mandatory for CC-licensed images.)

Note for future: we should have an info page (under info.laji.fi) which instructs users how images can be used. We get many questions about how images can be used, from people who don't know what CC-license is.