DiscreteBoundaryOperator::apply() accepts now matrices (not only column vectors).
Implemented the surface gradient.
Added the Laplace-Beltrami operator.
Added a discreteDenseBoundaryOperator() function together with Python wrappers.
Rewrapped some Python docs.
Added unit tests of the apply() function taking matrices.
Merge branch 'master' of github.com:bempp/bempp