Tx-XMPP 0.12 has beaking change in `discoFeature.identities` because it now supports
`xml:lang` attribute, so this update implies updating the code everywhere were this is
used.
- Implement `presence` access model for PEP nodes.
- Add PEP auto-subscription (`+notify` handling)
- New `get_pep_last_items` storage method to retrieve in a single query items to send to
auto-subscribers.
- Online resource tracking.
This completes the PEP support.
rel 476
New implementations of XEP-0355 and XEP-0356 are integrated to handle PEP. The
implementation is not complete yet, as auto-subscribe and presence permissions are not
implemented yet.
rel 476
