When searching allow use of uppercase locations

When searching allow use of uppercase location names, such as AUTHOR
instead of author, automatically lowercasing them. Fixes #1192785 [search errors are replicated automatically](https://bugs.launchpad.net/calibre/+bug/1192785)
Add a test for uppercase locations
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Confirm when dropping files onto Book Details

When dropping files onto the Book Details panel, ask for confirmation
before adding the files to the book. The confirmation can be disabled.
Fix unable to change case for search queries

Fix unable to change the case of a previously used search because of the
search history.
HTMLZ Output: Fix handling of images with URL unsafe filenames

Fixes #1192687 [htmlz output not rewriting img and urls](https://bugs.launchpad.net/calibre/+bug/1192687)
DOCX Input: Add support for images used as bullets
Fix caching of images in docx to use filenames instead of possibly
non-unique relationship ids.
Ebook-viewer: Show docx cover, if present
Update The Walrus Mag

Fixes #1193021 [Update recipe The Walrus Mag](https://bugs.launchpad.net/calibre/+bug/1193021)
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version 0.9.36