recovery: style cleanups
recovery: comment and log cleanups
recovery: removed heavyweight logging to speed up recovery
recovery: immutable kw argument
recovery: removed unused includes
recovery: do not touch routes from different group
recovery: use one container per key range
recovery: protect against really short routing tables
iterator: simplified IteratorResult class
recovery: move range subroutine to ranges.py
recovery: formatting
recovery: reformatted IteratorResult methods
recovery: added RouteList addresses method
recovery: more intuitive formatting for timer intervals
recovery: merge: use many ranges in single iterator

This greatly speeds up iteration process esp. on multi-terrabyte
storages with many route table entries.
recovery: do not filter result in python

Statements like:
    if result.id_range.start <= record.response.key <= result.id_range.stop:
are very slow in python esp. when executed many millions and potentially
billions of times.

So now we are putting all results in one big iterator result.
recovery: import unlink when needed
recovery: prepare for multiprocess split
recovery: process all remote iterators in parallel

TODO: For now Stat object is not picklable - will fix it in later
releases.
recovery: improved log message formatting