* `ProxyVerificationContractStorage` uses Proxy contract as a cosigner.
* `ProxyVerificationContractStorage` recreates a contract storage for each handler
invocation because of an issue: rpc-actor from morph client may be expired. This
way won't create a bottlenecks because it is expected that this contract storage
implementation will be used not so often.
* Make morph client return `RPCActor` (that is websocket client in fact).
* Make `SwitchRPCGuardedActor` return `RPCActor` as it will be used for
`ProxyVerificationContractStorage`.
Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>
