Some paths are too long

[MaxVerevkin]

For example rustbus::wire::unmarshal::traits::Variant. Variant is not even a trait, so this could be rustbus::wire::unmarshal::Variant. Same for rustbus::wire::marshal::traits::Variant.

Similarly rustbus::wire::marshal::traits::SignatureBuffer could be rustbus::signature::Buffer.

[KillingSpark]

The location of these files is based on the separation of this library into params and traits. I'll think about how to organize this better especially with the prospect of eventually retiring the params part of things.

[MaxVerevkin]

The location of these files is based on the separation of this library into params and traits

Now it makes sense :)