Add command 'remove' command to dynamic config

[peterdragun]

We have commands for dynamic config, which works good enough, but when we want to remove a value from a list, we have to copy the original list, modify it, and set the whole list. It would be nice to have a command that would be able to remove a value from a list. Basically, a reverse operation of the config append command, but it should be able to remove any element. We need to make sure that this would be only be supported on config values that are lists.