Sync with current NEO in Python implementation as the first step.

We'll be using some common bits and in particular on-the-wire protocol
must be the same and for py/go interoperability testing we'll also need
python parts.

This information is handy to see how well cache performs.

Amended by Julien Muchembled:
- do not abbreviate some existing field names in repr result (asking the
  user to look at the source code in order to decipher logs is not nice)
- hit: change from %.1f to %.3g
- hit: hide it completely if nload is 0
- use __future__.division instead of adding more casts to float

INFO Z2 Log files reopened successfully
INFO SignalHandler Caught signal SIGTERM
INFO Z2 Shutting down fast
INFO ZServer closing HTTP to new connections
ERROR ZODB.Connection Couldn't load state for BTrees.LOBTree.LOBucket 0xc12e29
Traceback (most recent call last):
  File "ZODB/Connection.py", line 909, in setstate
    self._setstate(obj, oid)
  File "ZODB/Connection.py", line 953, in _setstate
    p, serial = self._storage.load(oid, '')
  File "neo/client/Storage.py", line 81, in load
    return self.app.load(oid)[:2]
  File "neo/client/app.py", line 355, in load
    data, tid, next_tid, _ = self._loadFromStorage(oid, tid, before_tid)
  File "neo/client/app.py", line 387, in _loadFromStorage
    askStorage)
  File "neo/client/app.py", line 297, in _askStorageForRead
    self.sync()
  File "neo/client/app.py", line 898, in sync
    self._askPrimary(Packets.Ping())
  File "neo/client/app.py", line 163, in _askPrimary
    return self._ask(self._getMasterConnection(), packet,
  File "neo/client/app.py", line 177, in _getMasterConnection
    result = self.master_conn = self._connectToPrimaryNode()
  File "neo/client/app.py", line 202, in _connectToPrimaryNode
    index = (index + 1) % len(master_list)
ZeroDivisionError: integer division or modulo by zero

It's not possible yet to replicate a node that is importing data.
One must wait that the migration is finished.

The project to implement NEO storage and probably other pieces in Go
with the goal to have much lower request-reply latencies and
much better scalability when serving many clients compared to NEO
implemented in Python.

This reverts commit d3c22487 partially
and fixes the bug in a much simpler way.

Traceback (most recent call last):
  [...]
  File "neo/storage/handlers/client.py", line 115, in askStoreObject
    *e.args)
  File "neo/lib/handler.py", line 333, in queueEvent
    self.sortQueuedEvents()
  File "neo/lib/handler.py", line 326, in <lambda>
    self._event_queue.sort(key=key))()
  File "neo/storage/transactions.py", line 67, in __lt__
    return self.locking_tid < other.locking_tid
AttributeError: 'NoneType' object has no attribute 'locking_tid'

Pending events:
  (None, <askFetchTransactions: ...>)
  (<Transaction(C13, locking_tid=03c266508a058388, tid=None, age=0.21s) at 0x7f086bbc3d50>, <_askStoreObject: ...>)

It was out-of-date since commit 23b6a66a.

This time we had issues with _getObject and getReplicationObjectList
on production.
It seems related to the upgrade of MariaDB, from 10.0.21 to 10.1.25.

See also commits eaa00a88
             and 13911ca3

The explanation became wrong during a git-rebase, when it was decided
to keep the old code that drop partitions. The new one needs more work
and it is kept in a branch.

Using NEO 0.9.1 and partitioning enabled, I could reproduce the issue with
MariaDB 5.3.5, but not with MariaDB 5.3.12 and 5.5.23. I suppose it was fixed.

In testOudatedCellsOnDownStorage,
  'select count(*) from obj' returned a wrong value (always 1).

Strangely, 'select count(*) from test_neo0.obj' was always correct (102).

When 'neo.tests.cluster' is loaded (usually when functional tests are run),
__builtin__.pdb is replaced by an extended pdb, which should behave the same
way if it is used like the former.

winpdb is so slow that a console pdb is often preferred.