Parsing should not depend on std #26
Description
There are some instances where parsing of structs (core::str::FromStr) makes use of the implementations provided by the standard library. Problematically, these are defined in std and not in core such that this depends on the std feature. This makes the trait implementations inconsistent and makes the dependency quite a lot heavier.
Instead, such parsing should be implemented in a standalone version (possibly with a dedicated, small dependency).