Replaces Stacktraces with useful error messages.

Changed the message shown when a user doesn't enter project/tenant
id/name to be more informative.

When attempting to stat a container without supplying project/tenant
name or id, an empty response was being returned instead of an error
being raised.

Changed the error raised in swiftclient.client when no tenant or project
is specified to be more specific.

Add tests for basic regression checking.

Closes-Bug: #1372589

Change-Id: I4eb6964d9f1702db119cc0294edc02841b1ecd5f