Initial conditions for Gubser test

[jordissm]

The current initial conditions and subsequent time steps for the evolution of Gubser flow with shear viscosity, derived in Phys. Rev. C 91, 014903, were taken from MUSIC.

In order to have more flexibility in the comparison between the numerical and semi-analytical results, we should have a script to generate initial conditions from the ordinary differential equations in the paper.

[jordissm]

A pull request was done in #18 where a Mathematica script that tabulates the Gubser flow solution with shear was added to the misc directory.

[ominusliticus]

I will add here that there is a separate repository in the-nuclear-confectionary organization called viscous_gubser_BSQ which is a python script that implements viscous gubser with conserved charges, which can be run ideal and/or without currents.