Code removed from ReaderGesture and put into BookInfo where
it belongs, so we can just use Events.
Also convert description to plain text to not show HTML tags.
cre:loadDocument() may fail in recognizing the document format, and
koreader would previously keep calling other methods on it, which would
make crengine segfaults. We now check loadDocument success at the
various places it is called, and try to deal the best way we can when it fails.
So an image file can have a cover in coverbrowser's display.
It also allows for an alternative viewer (ImageViewer widget)
when holding on file / View full size cover.
- 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).
