Made the onHold buttons table similar to the one of File browser.
Added "Purge .sdr" and "Delete" to these buttons.
Moved the purgeSettings and removeFileFromHistoryIfWanted
logic into filemanagerutil functions.
Stay on the same page when manipulating history (previously, we were
always put back on first page).
Really keep deleted files in history (unless setting says otherwise).
Show deleted files in grey or dimmed in classic History and all
CoverBrowser display modes.
- Factored out duplicate code from filemanager.lua and filemanagerhistory.lua
to new filemanagerbookinfo.lua (and other common code to filemanagerutil.lua).
- Uses sidecar files' new doc_props and doc_pages settings, or fallback to
old 'stats' settings, or to opening document.
- Shows filename, filetype and directory.
- Shows description (Hold to see whole truncated text), keywords, and
cover image (tap to extract image from document and display it if available).
- Book information now available from reader menu, to display info about
the currently opened book.
- Convert possibly HTML description to plain text via added
util.htmlToPlainTextIfHtml() (for simple HTML conversion).
