-fixes for complex types:
- a structure which contains an enum from namespace 0 can not be created. fixes#1561.
- a structure with multidimensional array may lead to a endless loop in `ComplexTypeSystem.Load`
- a malformed namespace Uri which contains a space character prevents creation of type system.
- select endpoint doesn't pick the right scheme if the default endpoint must be picked
-prep for net472 or greater and net5.0 or greater build, only build #ifdef