Allow user to specify headers at the command line.
Allow user to specify headers at the command line.

Currently swift client does not allow content type to be specified
when upload an object. It does not allow a user to change content
type neither. This patch will allow a user to specify content
type by using upload command or modify the content type by using
post command.

For example:
1. To upload an object with specific content type:
swift upload -H content-type:applicaiton/xml con1 file1

2. To modify an object to a specific content type:
swift post -H content-type:application/josn con1 file1

This patch also allow a client to specify other request headers.

Change-Id: I12db83a1d465285e0906889cc67dfaa44e059568
Fixes: bug #1154621

JioCloud/python-swiftclient,VyacheslavHashov/python-swiftclient,varunarya10/python-swiftclient,citrix-openstack-build/python-swiftclient,jeseem/python-swiftclient,citrix-openstack/build-python-swiftclient,ironsmile/python-swiftclient,citrix-openstack/build-python-swiftclient,JioCloud/python-swiftclient,krnflake/python-hubicclient,pratikmallya/python-swiftclient,sohonetlabs/python-swiftclient,openstack/python-swiftclient,jeseem/python-swiftclient,openstack/python-swiftclient,citrix-openstack-build/python-swiftclient,ironsmile/python-swiftclient,sohonetlabs/python-swiftclient,iostackproject/IO-Bandwidth-Differentiation-Client,zackmdavis/python-swiftclient,iostackproject/IO-Bandwidth-Differentiation-Client,citrix-openstack/build-python-swiftclient,varunarya10/python-swiftclient,zackmdavis/python-swiftclient,VyacheslavHashov/python-swiftclient,pratikmallya/python-swiftclient