[domaindescriptions] add CircleDomain
[grids.oned] add ability to identify left and right boundary
[domaindiscretizers.default] add support for CircleDomain
[analyticalproblems] rename BurgersProblem -> Burgers2DProblem
[analyticalproblems] add BurgersProblem
[discretizer] add support for 1d problems in discretize_nonlinear_instationary_advection_fv