* Refactor nimbus_signing_node to support Unix signals.
* Fix SN unable to close REST server properly.
* Fix `keys`, `deposit` and `validator_registration` endpoints issues.
Add getValidatorExitSignature() and getDepositMessageSignature() to validator_pool.
* Add /reload endpoint and implementation.
Fix signData to not cancel `timer`.
Fix validator_pool should clear attachedValidators table.
* Diva protocol enhancement implementation.
Eugene Kabanov