Fix #1238636 [Calibre 1.6 / Find Duplicates Plugin /ERROR: Unhandled exception: <b>ValueError</b>:tuple.index(x): x not in tuple](https://bugs.launchpad.net/calibre/+bug/1238636)
Merge branch 'master' of https://github.com/cbhaley/calibre

Fixes #1238887 [Smart Device Control failes with Errno 2 No such file or directory:  <path>\\AppData\\Local\\calibre-cache\\device_drivers_SMART_DEVICE_APP_metadata_cache.json'](https://bugs.launchpad.net/calibre/+bug/1238887)
Robustness improvements
Show full path to the format file in a tooltip when hovering over the
link to open the format in the book details panel
Option to hide displayed cover size in edit metadata dialog

Edit metadata dialog: Allow turning off the cover size displayed in the
bottom right corner of the cover by right clicking the cover and
choosing "Hide cover size". It can be restored the same way.
Make shortcuts config file a variable
pep8
Add Open Book action
...
Robustness improvements in smart device driver