Add checks for meta cover tag and OPF package identifier
recipe update
Update various Polish news sources

Merge branch 'master' of https://github.com/fenuks/calibre
Fix user manual documentation for calibredb set_metadata incomplete
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version 1.20
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Trim changelog
Change emblem for duplicates to error symbol
Edit book: Allow editing of .plist files as XML
Fix #1266079 [eBook Reader "ImCoSys imcoV6L" not detected by calibre](https://bugs.launchpad.net/calibre/+bug/1266079)
Edit book: Prevent arrange into folders tool from moving files inside the META-INF folder
Refactor the workaround for QPlainTextEdit's mangling of nbsp into a separate class
Add in a default implementation of the event() override
Start work on diff view
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Syntax highlighting for the diff view
Fix first line being lost in diff view
Add line numbers to the diff view
Update New York Review of Books