R1:3ded757e847b

Implement more configuration options

Summary:
Allow extra options to be locked, hidden or masked via config. These options are themselves locked and can not be edited via the web UI.

The primary goal here is to let us lock or hide things from SaaS installs (e.g., keys, etc.), or to let server administrators lock or hide information from web UI administrators if they want to for some reason.

The secondary goal is to remove the `darkconsole.config-mask` option, although I might just remove the panel…