libtizplatform: added tiz_map_key_at and renamed tiz_map_at -> tiz_map_value_at
libtizplatform: moved OMX metadata retrieval from urcfgport to configport.
libtizonia: added basic support for metadata extraction in tizkernel (tiz_krn_clear_metadata and tiz_krn_store_metadata). Closes #85.
http_source: enabled use of the OMX metadata extraction APIs now implemented in libtizonia.
tplay: client graph now uses OMX_IndexConfigMetadataItem to retrieve the icy headers.