[API] Add new GetMetaData Media Object API

based on review, this version adds the missing break and also remove an unused test and goto label. (also done in GetUploadIDs from which it was inspired).
----------
- Add a new method GetMetaData to the org.gnome.UPnP.MediaObject2 interface to allow
the retrieval of the Meta data information of an object in DIDL-Lite XML format.
- MediaConsole python test app updated.
- Doc updated.
- Fix issue https://github.com/01org/dleyna-server/issues/25

Signed-off-by: Christophe Guiraud <christophe.guiraud@intel.com>