Output error or warning if ipdevpoll job plugins are configured in non-recommended order

[lunkwill42]

          For a follow-up PR you could make a validation error if this is spotted when reading/validating the config file.

Originally posted by @hmpf in #3254 (comment)

[lunkwill42]

Users are free to configure plugins to run in whatever order they like in ipdevpoll.conf, but sometimes plugins will have some preference or dependency on another plugins that would make it a bad idea to run them in random order.

Perhaps we need a system whereby a plugin can declare a preferred run-order compared to another, which could be used by ipdevpoll to refuse to start if they are not configured in that order in the config file.

The original suggestion was to make this a configuration error, i.e. make ipdevpoll refuse to start if the configuration is not up to snuff. I might also suggest then to add a command line option to convert plugin order errors to warnings, allowing the program to start regardless, just logging a warning for every "violation".