Rust Map based on Vec for serialization purposes

Made mainly for deserialization speedup, because deserializing to an actual HashMap is a lot slower. It also saves the original order of the data.

Usage examples: to deserialize and then .into_iter(); or to transfer data between different storages.

Also it has a trait SerdeMapStrategy, which helps to process data (currently only keys) at the serializing/deserializing stage, before saving to the inner Vec (example in docs).