[tmp] initial commit of the channel cube code
Switch to a new mode of handling the recirculation buffer.
Disable unused code for the recirculation buffer.
Add the original mako code for the recirculation buffer.
Remove unused recirculation kernel code.
Simplify the Reynolds stats kernels.
Clean up the channel cube example a little more.
Fix make_scalar_field.
Change computation of the viscosity in the cube example.
Make sure domain sizes are the same in the geometry class and in the
simulation class. Fix orientation for the outflow nodes.
Lower the max speed in the channel cube example.