* DoxygenLayout.xml: Set mainpage title
* libwget.doxy.in: Scan docs, add mainpage.md as main page
* mainpage.md: New file
* faq.md: New file
* wget2_manual.md: New file, derived from wget.texi
* docs/gen-logo.sh: Add script to generate logo via imagemagick
* docs/wget-logo.png: Add generated logo
* docs/libwget.doxy.in: Include logo into docs