Simple WebSockets notification about new request (#1202)

* Splitting methods requiring signing into separate trait

* Single place where RPC apis are created.

* Separating eth_filter

* Separating eth_signing

* Stubs for Personal Signer methods

* Test for EthSigningQueueClient

* TransactionConfirmation API

* Exposing PersonalSigner API

* Defining ApiSets dependent on context

* Removing types

* Supporting sending notification to WS connected SystemUIs

* Sending a notification on every new messages

* Adding logs to signing queue

* Shutting down broadcaster

* Refactoring the signing queue

* Fixing wait loop in case of spurious wake-ups.