ncm-metaconfig: add ability to do service reload

[alahiff]

It seems that ncm-metaconfig can only restart a specified service when the configuration is changed. This is a blocking issue that prevents us from being able to use metaconfig for some services, e.g. HTCondor. Would it be possible to add the ability to do a service reload?

[piojo-zz]

As agreed during the workshop, we'll modify the schema slightly so that each file contains an nlist of daemons and actions:

"/.../metaconfig/services/{/path/to/fie}/daemons" = nlist(
    "daemona", "action_for_daemona",
    ...
);

If two files require different actions on the same daemon, we'll execute them all at the beginning. In the future, depending on the need, we may de-duplicate actions.

[stdweird]

we need feedback how to treat the use of the legacy daemon field: do we throw a warning (maybe even in the schema validation) and thus treating it as real legacy code? if so, we should also schedule a traget release by which this becomes an error (and not allowed in schema).

[jrha]

Fixed by #328.