Debug output should include user-readable enum names

Submitted by David Laban @alsuren

Assigned to Telepathy bugs list

Link to original bug (#37803)

Description

I have a little WIP at http://cgit.collabora.com/git/user/alsuren/telepathy-glib.git/log/?h=human-readable-enums

current issues:

I don't know how much space this takes in the tp-glib binary (quite a lot)

it breaks g-i because some namespace fail in NUM_TP_CONTACT_METADATA_STORAGE_TYPES etc.

Version: git master