setAttribute("archive", 1) sets this attribute to "true", and

setAttribute("archive", 1) sets this attribute to "true", and
getAttribute("archive") returns 1 if the attribute is set, and 0 otherwise.

Allow to query and to set all properties by not specifying an attribute
string:  getAttribute() returns all attributes bit coded in an integer,
and setAttribute(attr) sets all attributes. No assumptions may be made
about the meaning of the bits -- they can be changed in future fgfs releases.
The only valid use is to compare or set attribute numbers obtained in the
same fgfs run. This is meant for allowing full copies of property branches.
Also add getAttribute query strings "children" for the number of children,
and "alias".