OpenSystemsDevelopment / qpdf

Also, reject them in strings.

Also. remove '.' as  starting char in lsTop.

Avoid representing as PDF Doc encoding any string whose PDF Doc
encoding representation starts with a UTF-16 or UTF-8 marker.

Since Buffer has always implemented its copy constructor with a deep
copy, its Members object will never have multiple owners. Change to unique_ptr.

Also implement move constructors for Buffer, since there may be cases
where a deep copy is not needed.

When the schema wants a variable-length array, allow a single item as
well as allowing an array.

I decided these were confusing and inconsistent with how JSON works.
They muddle the API rather than improving it.

Call the parent container's item method before calling the child
item's start method so we can easily know the current nesting level
when nested items are added.

Update getJSON() methods and calls to them