recovery: make response_data property too
recovery: introduce Ctx class to store config
recovery: pretty print for Time
recovery: reworked stats

Still new implementation is needed (probably in separate class) to hide
this ugliness.
recovery: put node and elog into ctx
recovery: use provided temp dir
recovery: code cleanups
recovery: remove lock comment - user should use flock/lockf
recovery: fixed comment
recovery: more verbose logging
python: added bulk_read_by_id() API

Also added alias from bulk_read() to bulk_read_by_name()
recovery: bulk read/write resulting diff's
recovery: replaced manual caching with backported lru_cache
recovery: optimize computing off diff for empty local or/and remote containers
recovery: fix variable shadowing in recover()
recovery: fixed --groups option
recovery: set default timeout to 3600
recovery: improved comments
recovery: simplify dnet_iterator_response_container_diff()
recovery: simplify flag handling in elliptics_create_session()