Add Euler equation (very preliminary)
Separate out Euler equation calculations in preparation for hydro and fix scheduling
euler_test.par: Add dissipation and some ID parameters
kranc.th: Add dissipation thorn and include only Euler example
Euler.m: Schedule RHS calculation only in the interior of the grid
Euler.m: Add shock tube initial data
Advect.m: Add advection equation
Burgers.m: Add Burger's equation with minmod reconstruction and HLLE Riemann solver
kranc.th: Add Advect and Burgers
Differencing.m: Add DiffPlusOp and DiffMinusOp

These operators take forward and backward differences without dividing by the grid spacing.
Differencing.m: Throw an error if the FD operator definition does not match the pattern

Previously Kranc silently generated nonsense code
Differencing.m: Make FD operator pattern more generic

Previously it required a grid spacing to be present; now it does not
Add calculation option ApplyBCs

This option forces Kranc to put the calculation in a group and select and schedule boundary conditions directly after the calculation is called.
Burgers.m: Fix to use the correct uR in HLLE
Burgers.m: Correct sign errors, fix minmod and add comments
MathematicaCompat.h: Add MinMod function
kranc.th: Use KrancHydroNumericalTools to pick up the right branch
Euler.m: Replace standard finite differencing with conservative method (minmod and HLLE)
Examples: Add hydro parameter files
Euler.m: Fix to use reconstructed En