Disambiguate terminology for "storage" #38
Description
Currently storage refers to two different concepts. In the public API, "storage" only refers to the actual data structure that holds the components (i.e. VecStorage and storage::Tree), but internally it is also used to refer to the storage wrapper types for simple and isotope components (i.e. storage::Simple and storage::IsotopeMap). We should rename the latter to something else like "storage wrapper" etc.