Add a new diagnostic algorithm for viscous dissipation which works in 2D and 3D, but assumes a constant viscosity tensor. Modify energy stats tests to use this new algorithm.
Remove all evidence of old viscous dissipation algorithm. The more I looked at this the more it concerned me. There was no viscosity term used at all and to me it looked like it was computing an incorrect definition of the strain rate tensor.
As the viscous dissipation calculation inside fluidity now includes the viscosity, there is no need to multiply by viscosity in the .xml file.
Merge pull request #8 from FluidityProject/fluidity-viscous-dissipation

Fluidity viscous dissipation