Diagnostic tweaks
Merge branch 'master' of https://github.com/GRiker/calibre
Fix #1298071 [[Edit book]: Crash exporting image](https://bugs.launchpad.net/calibre/+bug/1298071)
Fix #1298404 [Untranslatable string "Copy Link"](https://bugs.launchpad.net/calibre/+bug/1298404)
calibre-customize help: Do not error out if one of the installed plugins has no customization help
Edit Book: When generating an inline ToC add a class attribute to all <ul> tags to make it easy to style a particular level of the ToC
Fix unnecessary error when shutting down GUI IPC socket on linux
Fix abstract named socket used for GUI IPC on linux not being shutdown till process exit, thereby preventing restart from working. Fixes #1298756 [error restarting](https://bugs.launchpad.net/calibre/+bug/1298756)
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version 1.30
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Prevent ImageMagick crash in identify when debugging MOBI6 files
pep8
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pep8
Make MOBI/AZW3 output a little closer to that of current kindlegen
pep8
Fix regression that broke ebook-device cp
AZW3 Output: Fix a bug that caused popup footnotes in some AZW3 files to not work properly. The popup would show all remaining footnotes instead of only the current footnote. Fixes #1293290 [popup Comments can not be displayed correctly in azw3 file](https://bugs.launchpad.net/calibre/+bug/1293290)

This was caused by the offsets to links in the AZW3 generated by calibre
to be slightly incorrect, confusing the heuristic algorithm used by the
kindle to detect footnote extents.