[proposal] Implement jms/metadata on all bundles that use "metadata"

[dantleech]

This is just something that I think would be awesome post 1.0.

At the moment all the CMF bundles actually do Document metadata mapping through the DI config.

I suggest that we refactor all such bundles to do this through jms/metadata, preserving BC, but adding the possiblity to easily add support for annotations or separate XML/YAML/PHP mapping files.