Worker Proposals can be posted without a reference to a description of the proposal. It should be possible to update the reference regardless of the state of the worker proposal. There are also cases where proposed workers that fail to get voted in or get superceded by another worker continue to be visible. This isn't a huge problem at the moment, but it is an important housekeeping operation as we move forward.
# Motivation
Having clearly defined eligible proposed and active WP's is critical to proper governance.
# Rational
Either Committee or WP Issuer should have the abiity to retire a WP. I could make the argument that the WP Issuer should be able to retire their WP at any time whether it's active or not.
* Add check to `db_maint.cpp` to skip workers in removed state.
* Don't allow votes to workers in removed state(`account_evaluator.cpp`).
* Create operation `worker_update`. Op will allow to change only the `url` and the `removed` object fields from the worker (track the change in operation). Can follow `committee_member_update` or similars.
* Implement new operation as a command to `cli_wallet` available for the worker issuer.
