[common.color] replace toString with std::to_string
- there was an cyclic inclusion color.hh -> string.hh -> ... -> color.hh
- for int, it is no advantage to use toString instead of std::to_string
[common.parameter.configcontainer] reorder member variables to match initialization order
[common.string] fix unused variable warnings
[grid.information] fix unused variable warning
[test.common_string] remove check for nested containers
[grid.provider] use 4D-coordinates for default config, disable 4D test for now