Updated TupleWithMeta class to make it consistent with other Meta
classes in order to avoid confusion. Also made provision to call
TupleWithMeta with a tuple containing one or more elements.

For more details on how request_id will be returned to the caller,
please refer to the approved blueprint [1] discussed with the
cross-project team.
[1] http://specs.openstack.org/openstack/openstack-specs/specs/return-request-id.html

Change-Id: I5a79a4ed8cb4dc83ea3b64499df191750462100d
Partial-Implements: blueprint return-request-id-to-caller

Added wrapper classes which are inherited from base data types list,
tuple and dict. Each of these wrapper classes contains a 'request_ids'
attribute which will be populated with a 'x-openstack-request_id'
received in a header from a response body.

This change is required to return 'request_id' from
client to log request_id mappings of cross projects.

Partial-Implements: blueprint return-request-id-to-caller
Change-Id: I3aadb4d8bf675e20f2094b66a23ac20f455a99eb

Many clients have to_dict method in Resource class.
It is needed to get full info about resource.
So it would be nice to add to_dict method in
cinder client too.

Now openstack/common has graduated from oslo-incubator.
So we just modify it cinderclient.

Changes merged with this patch:
---------------------
apiclient/base.py
  ---add to_dict function in class Resource.
unit/test_base.py
  ---add unit test case.

change-Id: I81add424bcdd667ba271adb7d5b1ceb504120f93

This is the first step of moving functional testing
into the project tree.  This change just moves
all of the unit tests to be under a dedicated tests/unit
directory.

Follow up patches will add the functional directory and
start moving tempest CLI tests there.

Change-Id: I9dc0b8f761676c1b3bbdeb03e2f44b35f75c693e