1.6.5 released improved large library search and more

[setherd]

Search every synced Calibre library and Downloads at once from the top of the library drawer. Results are grouped into collapsible library sections, saved books are marked, and Calibre Server libraries clearly show when only an offline copy is available.
Very large libraries (80,000+ books) now load smoothly instead of freezing or crashing.
Each library and the Downloads screen remember their own sort order, so switching between them no longer resets how your books are arranged.
OPDS catalogs now share one consistent set of browse controls and keep your place when you page through a catalog.
A mistyped WebDAV address now fails fast with a plain-language message and can be corrected in place instead of locking you out of setup.
Misc fixes