add csg.getFeatures(features) where eg features = [‘volume', 'area’]

function takes array of one or more features as an argument.

“getFeatures” can calculate any csg features that can be expressed as a (signed) sum of features of its
constituent tetrahedrons.
Currently only volume and area are implemented, but others (fourier coeff, moments) could be
added.

For performance reasons, the function is designed such that it can calculate multiple features in a single pass.