Get nodes/normals directly from the discretization collection

examples/advection/surface.py

examples/advection/var-velocity.py

examples/advection/weak.py

examples/geometry.py

examples/maxwell/cavities.py

examples/wave/var-propagation-speed.py

examples/wave/wave-min-mpi.py

examples/wave/wave-min.py

examples/wave/wave-op-mpi.py

examples/wave/wave-op-var-velocity.py

examples/wave/wave-op.py

grudge/models/advection.py

grudge/models/em.py

grudge/models/wave.py

test/test_grudge.py

test/test_mpi_communication.py

test/test_op.py