plugin XEP-0060: MAM integration: - removed useless XEP-0059 recommendation - added XEP-0313 as a recommended plugin - parseExtra now manage mam_* keys (mam_filter_[name] to use a filter) - if a mam request is in 'mam' key of extra parameted in getItems, a MAM request is done, but the result is returned in the same way as for normal getItems, making like more easy for other plugins and for frontends