Share type refactor

[fl0rek]

Share type refactor - when we introduced our Share type, we required it to have a validated namespace. In retrospect this might not have been a right decision, as all parity shares are treated as if they had PARITY_NAMESPACE, despite the actual value being random bytes coming from leopard codec. This meant that wherever share could be a parity share we couldn't use our typed interface and had to fall back to plain vectors of bytes with custom logic.