Add keystone v3 auth support

Enables swiftclient to authenticate using
the keystone v3 API, allowing user id's, user
domains and tenant/project domains to be
specified.

Since swiftclient imports keystoneclient, the
main changes in swiftclient/client.py are to
selectively import the correct keystoneclient
library version and pass a number of new
options to it via the get_auth() function. In
addition the get_keystoneclient_2_0 method
has been renamed get_auth_keystone to better
reflect its purpose since it now deals with
both v2 and v3 use cases.

In swiftclient/shell.py the new options are
added to the parser. To make the default help
message shorter, help for all the --os-*
options (including the existing v2 options)
is only displayed when explicitly requested
usng a new --os-help option.

A new set of unit tests is added to
test_shell.py to verify the parser. A comment
in tests/sample.conf explains how to
configure the existing functional tests to
run using keystone v3 API.

Note that to use keystone v3
with swift you will need to set
auth_version = v3.0 in the auth_token
middleware config section of
proxy-server.conf.

Change-Id: Ifda0b3263eb919a8c6a1b204ba0a1215ed6f642f
Merge "Add keystone v3 auth support"