Feature/inc ns dg kernel

This branch introduces a new SVV kernel which more accurately mimics the diffusive properties of DG from the perspective of spatial and temporal dispersion analysis. This SVV also introduces a new local h and P scaling for each element and also permits the one to specify a velocity (for example using an average field). The spectral vanishing viscosity tag is DGKernel.

Since the SVV parameters vary on each element in this branch I have had to extend the parameters that are passed to GlobalLinSys so that now the sovler can receive a list of doubles per element.

Closes #60 (closed)