newdb: Handle databases that have empty author records

Fixes #1218465 [Can not Edit Metadata](https://bugs.launchpad.net/calibre/+bug/1218465)
newdb: Automatically sanitize ratings tables that contain rating records
Update Instapaper
Use approx_formats when creating the formats column

Have the template used for the formats column when clicking the Formats
shortcut in the create columns dialog use approximate_formats() instead
of formats.
Amazon metadata download: Update to handle website changes at amazon.com
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Various translation fixes

Fixes #1219227 [Enhancement and missing translation strings](https://bugs.launchpad.net/calibre/+bug/1219227)
Edit metadata dialog: Add an undo option for the Trim cover button

See #1219227 (Enhancement and missing translation strings)
MOBI Output: Fix some sub/super scripts missing

MOBI Output: Fix conversion of some super/sub scripts failling if they
are the first or last element in a paragraph. Fixes #1218858 [Subscripted text is generated by chance (MOBI)](https://bugs.launchpad.net/calibre/+bug/1218858)
Fix chunking in libimobiledevice and remove obsolete logging code
Update Countryfile
Conversion: Handle invalid font-family when subsetting

Conversion: Fix font declarations with invalid font-family values
causing conversion to abort when subsetting is enabled.
Metadata editor: Fix adding an image to an empty comments block not working
Change thumbnail cache to use a LIFO queue

This should fix the problem of covers being rendered slowly at the end
when scrolling through a very large number of covers very quickly.
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PDF Output: Accept commas in custom paper size specification

Used in some European countries.
Fix test breakage caused by code to remove rating=0 entries
Speed up sorting when book list is showing a subset

Speed up sorting when the book list is showing a restricted set of
books, such as when the results of a search are displayed or a virtual
library is used. Fixes #1217622 [calculated column sorts update the entire database while inside a Virtual Library](https://bugs.launchpad.net/calibre/+bug/1217622)
Change quickview to not sort search results. They are sorted in QV's table.