Enhancement #1353954 - Select all buttons. Note that the button layout changed considerably.
Library check: Add buttons to conveniently mark all fixable/deletable items. Fixes #1353954 [Enhancement - In 'Check library' allow select all for extra titles, extra authors, etc](https://bugs.launchpad.net/calibre/+bug/1353954)

Merge branch 'master' of https://github.com/cbhaley/calibre