#233 Deal with the perfect forwarding problem

[Ulf Lorenz]

What and Why

Both the SubspaceTransformation and the Grid have the problem that you cannot construct their arguments on the fly together with std::make_shared, because this confuses the compiler.

Possible solutions: * specialize std::make_shared, but this is forbidden from C++20 (C++23?) onwards * somehow do something with an initializer_list? * use an own make_shared or something with a better name that by default forwards to std::make_shared