wmf: make swiftclient an optional dependency

Swift is only used when there is a [swift] configuration section, but we
always import the swiftclient module.

I can not use the switclient on my setup, so I thought about loading it
via extras just like we do for statsd to transparently ignore the
missing dependency.

Another way would be only import it when we have a [swift] section but
that makes it harder to find out that is an optional dependency.

Change-Id: Ie2ef84f86f9f57796a85758147ba87d8b22c3e55
wmf: soften requirements

WebOb and paramiko have a minimal version which is enforced by OpenStack
but is most probably not needed.

ordereddict is for python 2.6, the feature is included in python 2.7.

swiftclient/keystoneclient . A wmf hack to skip swift entirely.

Change-Id: I1aa1e3ae496d68d25dd64e8b21d2057c473342f4