Add a make target to build the API documentation zip archive
Add a make target to build the API documentation zip archive

The `ddist` target packages the generated API documentation into
a zip archive file suitable for uploading to PyPI.

Change-Id: Ib94f445d03bdb45e817355ef1ad0d8119e10a0d9

dpursehouse/pygerrit,dpursehouse/pygerrit2,gferon/pygerrit2,sonyxperiadev/pygerrit,morucci/pygerrit,benjiii/pygerrit,markon/pygerrit2