This fixes test_report_view (testDeferredStyle).

memcache module already handle thread-safety, and we actually want to be
transaction-local here, so use a volatile variable instead for caching
needs.
Removes the need to restart Zope for connection parameter changes to take
effect.
Fixes a bad interaction with SelectionTool's code, which causes
transactional isolation to be broken (just for this connector) and too many
network connections to be used.

Garbage-collecting memcache.Client instance does that automatically.

Docstrings are not to annotate what code is doing.

Concurrency handling is not required, because a single MemcachedDict should
not be accessed outside a Zope transaction, which is itself bound to a
specific thread.
Pickling a connection is not needed, ERP5Type.Core.MemcachedPlugin is all
we need to serialise.

Simplifies code creating a new connection.

Doc's mention about expiration time is precisely that server's code is
supposed to do just that internally.

See commit 4718f5e1

A ZopeLite patch was added to prevent loading of zcml files, which is wrong
for ERP5: CMF products were not properly initialized.

Code is also simpler now that we call OFS.Application.initialize(), which is
not significantly slower.

We keep patch not to register help though because this is quite expensive:
we should even consider always disable help because they seems to cause many
conflicts during Zope cluster startup.

A monkey-patch to unittest is updated for Python 2.7, so that tests aren't run
when they shouldn't (e.g. --save without --load).

app() creates a new transactional connection to ZODB, which triggers
scary (although innocuous in this case) connection pool warnings.
Instead, use getSite provided in ERP5 product and filled when
traversing site's portal. Retrieved acl_users object is different, but
this should not matter.
Also, to prevent import loop and to keep this change minimal, do a
local import.

line breaks are too special and generates weird layout (like when adjust is used)