Added default bookshelf name
Also use google for edition covers

LibraryThing covers API seems pretty unreliable these days (less user
covers, most likely). So we now fall back to Google. 

May want to make google the default and/or add goodreads as well.
Merge branch '5.1.1'
Fix donation links
Support for linkifying partial HTML strings and displaying hints only
once per instance
Amazon hint

Display the amazon blurb every 7 instances.
Added 5.1.1 section
Merge github.com:eleybourn/Book-Catalogue