Follow up for patch https://review.openstack.org/#/c/76487/

Change-Id: I6801b75cb78a3da0631ca8a60b7c2756b8930e72

To make bin/swift importable for testing it needs to be renamed/moved.
The final idea is to move it to swiftclient/shell.py and add only a stub
in bin/swift to import swiftclient/shell.py.

However, doing this in a single step makes reviewing very hard, because
now there are > 1400 lines deleted from bin/swift and added to
swiftclient/shell.py - Gerrit doesn't detect the moved file.

For example: https://review.openstack.org/#/c/73710/2/

This patch first moves the code to swiftclient/shell.py and uses
setup.py/cfg to create the stub file in bin/swift. A follow up
(https://review.openstack.org/#/c/76489/) will then add the stub itself
in bin/swift (and remove the entry in setup.py).

The change to tox.ini is related to bug 1290562 and can be removed in
the future.

Change-Id: Id86392ccaf09e1d80a5d808fb49827d6d18c2588

Make help strings more consistent:
* Fix wording and grammar, remove duplicated words
* Add "." consistently everywhere.

Change-Id: I37f94600df2a58532633f6bab2ab82fc5e91a75b

Change-Id: Ia07554250a6aae8f3a6be6a70f83690ec3fc108c

Keep the format of these strings constant through all options and commands.

Change-Id: I67a47bdd5681b4b221baf55933a175568aa8e16d

Have all the option help strinsg match the usage text for that command.

Change-Id: I575a71769600f95c33cc4bbc9904b313f890e997

Change-Id: I091b1d2de41ff59b21ce136738e2f69b759d682b