Just wondering... as a qpy html template in practice always returns
with a call to:

        h8.from_list( template_contents )

This means that in a hierarchy of qpy html template calls, each call is
building a list, then returning its joined contents as a h8 string,
potentially implying creating and throwing away many intermediate
strings.

Would there be any gains from either of these possibilities:

- Have a nested qpy html template always append to the caller's
template list, thus a "page" (or whatever, a sizable chunk initiated by
an "entry call" to a qpy template that calls other qpy templates) is
built by just building onto one big list. Thus returning from a nested
qpy template will not do any h8 concatenation. The return from the
"entry call" needs to know to concatenate... or maybe not, as the
context may deal with it happily (e.g. using it as a string will cause
the h8 concatenation to happen... while still allow to use it
explicitly as a list).

- Model qpy templates to be generators... similar concept to above, but
will affect how the calls are done. Thus the compiled qpy template will
look like a sequence of yield statements.

mario