swiftclient: add short options to help message
swiftclient: add short options to help message

- add usage strings for short option such as '-a' for '--all'
  This add all short options  to usage text.
- add missing --header usage help for download command
- some cometic changes

Closes-bug: #1475511

Change-Id: Ibfecac8764669540fa025787548133a50fa50b10
Signed-off-by: Hiroshi Miura <ff6fb3ed059786151e736af13627c08d24e9f922@nttdata.co.jp>

sohonetlabs/python-swiftclient,jeseem/python-swiftclient,openstack/python-swiftclient,ironsmile/python-swiftclient,openstack/python-swiftclient,VyacheslavHashov/python-swiftclient,ironsmile/python-swiftclient,sohonetlabs/python-swiftclient,VyacheslavHashov/python-swiftclient,jeseem/python-swiftclient