Error in density derivative fixed (neglected to multiply by density),
using factor of n for penalizing derivatives, feeding derivative of 1
when lbound.pd and ubound.nd are called
Added print class
Using idea gleaned from Kooperberg to generate bases appropriate for
density estimation by artificially adding knots, removing two bases
(second from left and right) to create smoothly declining bases.
Using -sqrt(.Machine$double.eps) for upper bound (suggestion of Kooperberg)