Improve the process of getting a handle to a specific wallet with `Kmd` about algonaut

[manuelmauro]

@i-schuetz do you have any idea about this? I am thinking that the crate algonaut_client might stay very low-level with functions almost 1-to-1 with Algorand's API, while improving the ergonomics in the parent algonaut crate or in a new one. In this case adding a struct with a function like get(wallet_name: &str).

[ivanschuetz]

Yeah, this shouldn't be added to the client. I'd probably create a v1::Kmd that wraps around the client and adds convenience like this. You could rename the current Kmd in KmdBuilder or similar.

[manuelmauro]

Great, seems a good solution! I only have mixed feelings on builders' naming convention. I noticed that reqwest follows this convention while crates like actix seems not to.