Stewards should be able to demote and promote their own node

A Steward needs to have the ability to demote and promote their own node. The use case is if a Steward knows they will be down for maintenance and they want to remove their node from the pool so it does not count as a failed node during down time.

The current process of removing a node from the pool is to send the following command

send NODE dest=<NODE ID> data={'alias': '<node name>', 'services': []}

Currently only a Trustee has the permissions to perform this action.
To add promote the node back into the pool the Steward would need to be able to send the following command

send NODE dest=<NODE ID> data={'alias': '<node name>', 'services': ['VALIDATOR']}