If we actually expect 3rd party applications to use libosmo-e1d to talk
to osmo-e1d, we'd better add some basic documentation on how this API
shall be used.
Change-Id: Ib4a97045bca276fbd3892f801898a436de7dc39b
prior to this patch, the configured vpair interfaces would not
be saved to the config file on 'write file'.
Change-Id: Iff6551318534a3717c374060082147f17b925a21