No real change. Reordering setting and dumping of attribute in the same
order (mostly) they are declared in book.h make it easier to detect missing
attribute.
The `common` name is from the time where kiwix was only one repository
for all the project (android, desktop, server...).
Now we have split the repositories and kiwix-lib is the "common" repo,
the "common" directory is somehow nonsense.
This feature is considered obsolete for a while.
In fact, it was already not supported since June 2018 as we were compiling
xapian without the chert backend support.
Assume that we don't support it and remove it from the code.
See kiwix/kiwix-tools#245
This is a API break. library.xml files will still work but the indexPath
and indexType will be dropped silently from the file.
`reader.getFileSize()` return the size of the zim in Kbyte in a
`unsigned int` (32 bits). This is ok as it would overflow if the size
of the size is greater than 4294967295 kbytes (so ~4Tbytes).
However, we need to convert the return size into a unsigned 64 bits integer
else, when converting to bytes, we will overflow at 4Gbytes.
Even in `m_size` is a uint64_t.
When parsing a opds feed, the favicon is a url, not a dataurl.
If we download the favicon all the times, it may take a lot of time to
parse the feed.
We store the url and download the favicon only when needed (when displayed)
