Add client man page swift.1

This is the byte-by-byte copy of swift.1 that was left behind
in the main Swift package when python-swiftclient was split away.
Apparently there is absolutely nothing to be changed in setup.py
and the distribution packagers are supposed to pick the page as-is
using their packaging systems.

Change-Id: I24f238501589db940574eac61b89a1422fe2fd77