[grids.boundaryinfos] add SubGridBoundaryInfo
[grids.subgrid] small enhancements
[operators.basic] add ComponentProjection
[domaindiscretizers.default] bugfix
[parameters.base] bugfix
[tools.inplace] bugfix
[operators.constructions] use projected() in project_operator if available
[operators.constructions] add Concatenation operator
[operators.fv] handle boundary conditions in NonlinearAdvectionLaxFriedrichs
[operators.fv] add NonlinearAdvectionEngquistOsher
[operators.fv] add L2ProductFunctional
[analyticalproblems] add InstationaryAdvectionProblem
[analyticalproblems] add BurgersProblem
[discretizations] add InstationaryNonlinearDiscretization
[discretizers.advection] add discretize_nonlinear_instationary_advection_fv
[demos] add burgers demo