Add a metadata service and a test

[jmcarcell]

BEGINRELEASENOTES

• Add a metadata service that is automatically added when importing IOSvc from k4FWCore, if no metadata is added then the service won't do anything. If metadata is added, the metadata service will hold a podio::Frame with the metadata that the Writer will write. The metadata service only works when there is an output file.
• Add a test showing an example of its usage
• Make changes in the MetadaHandle to make it possible to save and read metadata from DataHandle-based algorithms, so that when switching to IOSvc metadata for existing DataHandle algorithms will keep working. Add a test using IOSvc with DataHandle algorithms that write and read metadata.

ENDRELEASENOTES

[tmadlener]

Where do these parameters go? To the event frame or to the metadata frame? If the latter, I think this should be impossible. At least with the MetaDataHandle we went to some length to make this fail (at runtime), because if something is "true metadata" then it should be constant at file level. Hence, there should be no need to make it possible to even set this during event processing. If we can make this call go to the event frame, then it would be OK, I suppose, but it might be a bit confusing to have only one interface for doing both.

The notable exception for setting metadata during event processing is obviously the MarlinWrapper, but I don't think we should make this easily possible here, just because it's needed there.

[jmcarcell]

Now changed to prevent from putting parameters in the metadata frame as it was being done for the handle-based algorithms, it's literally the same mechanism so I think it should work for MarlinWrapper.

[jmcarcell]

This should now be ready and when using IOSvc it also works fine with DataHandle algorithms. I didn't bother with making it work when using PodioInput or PodioOutput and functional algorithms since that shouldn't be the case anyway.