calibre 0.8.52 released

• EPUB Input: When setting the cover for a book that identifies its cover image, but not the html wrapper around the cover, try to detect and remove that wrapper automatically.
• When deleting books of a specific format, show the number of books with each format available
• Linux install: No longer create MAN pages as all utilities have more comprehensive command line –help anyway
• Add a tweak Preferences->Tweaks to control the default choice of format for the Tweak Book feature
• Conversion: Allow setting negative page margins. A negative page margin means that calibre will not specify any page margin in the output document (for formats that support this)

Bug Fixes

• Tweak book: Fix handling of covers when tweaking KF8 books
• KF8 Output: Handle input documents with out of sequence ToC entries. Note that currently section jumping in the KF8 output produced by calibre for such files does not work.
• Edit metadata dialog: Fix the edit values button for custom tag-like columns showing a unneeded warning about changed values
• EPUB Output: Be a little more conservative when removing tags. Only remove them if they have actual forms inside.
• EPUB Input: Correctly update the Cover entry in the ToC even when the entry has a fragment reference.
• Update ImagMagick DLLs in all calibre binary builds to fix security vulnerabilities in ImageMagick
• Advanced search dialog: Fix equals and regex matching not being applied for custom column searches.
• RTF Input: Handle old RTF files that have commands without braces.
• Get Books: Diesel, fix results not showing when only a single match is found
• Get Books: Fix DRM status indicators for Kobo and Diesel stores. Fix smashwords not returning results.
• Fix regression in 0.8.51 that broke viewing of LIT and some EPUB files