As per the proposed changed in the sequence diagram.
The aim is to have a unique terminology per message instead of having
the same name for 2 consequent messages that share the same behaviour.
Note that the aim is to remove the shared `RequestResponse` behaviours.
Created network, storage and protocol modules. Organised
files into the modules where the belong.
xmr_btc crate moved into isolated modulein swap crate.
Remove the xmr_btc module and integrate into swap crate.
Consolidate message related code
Reorganise imports
Remove unused parent Message enum
Remove unused parent State enum
Remove unused dependencies from Cargo.toml
