Move namespace class definition out of PythonUI.
Make a comment more clear.
Correct the handling of empty labels.

Correct the handling of empty labels.  PythonUI erroneously closed boxes even if
they were opened without a label, in which case closeBox() could be called on
the last box.  Now PythonUI keeps track of boxes opened with an empty label and
does not pop the current name-space then.  This removes the need to check
whether the last box is being closed.
Add a comment.
Add support for parameters with an empty label.

Add support for parameters with an empty label.  These are put in a list
"anon_params" in the current name-space.
Implement PythonUI.declare().

Implement PythonUI.declare().  FAUSTDsp objects and their boxes/name-spaces and
parameters now reflect all meta-data declared by the DSP object.