Updated calibre to 2.57.1.

New Features
Driver for the Bq Cervantes 3
A new "Ornamental" cover design for the "Generate cover" feature
Windows: Use a helper process that does not load any calibre DLLs to display file open/save dialogs. This should fix most crashes caused by poorly designed windows shell extensions.
Allow pressing Alt+O as a shortcut for click the OK button in the Add from ISBN dialog.
Remove the calibre dependency on ImageMagick -- reduces calibre install size by ~ 15MB
Edit book: Add a new image filter: Normalize -- to improve the contrast in images
Edit book: Add a filter to make images look like oil paintings
Use 'Not rated' for zero stars in all rating spin boxes

Bug Fixes
Edit Book: Fix a crash in the Insert Link tool if one of the HTML files contains an empty id.
Fix tag like custom columns not sorted when displayed in the Book Details panel.
Fix transient window shown during Edit Book startup
Preserve booklist horizontal scroll position when merging books.
Google Images metadata download plugin: Fix error when searching for books with non-English characters in the title or author names.
Template language: Fix an error formatting dates when the underlying date does not have a day.
Preferences->Keyboard: Fix unable to use Alt+A and Alt+S as custom shortcuts.
Version 2.57.1 is a hotfix to fix a regression that broke conversion of ODT files in 2.57.0

(wiz)