Fix help of some optional arguments

Some positional arguments are optional but the help indicate
they are mendatory and can be confuse for an user.

  swift delete <container> [object]
  swift post <container> [object]

Change-Id: I7be525905b51d3ef160b0f47194e817b5cba0f9b
Merge "Fix help of some optional arguments"
Add --object-name

Add parameter --object-name, which:
1) Sets target object name when upload single file
2) Sets object prefix when upload a directory

Change-Id: Idc4357c3355e66d31c100540b901e70db20b03c3
Closes-Bug: 1012979
Merge "Add --object-name"