SYSV: Implement downloading and installing SYSV packages from HTTP

pkgadd has different syntax for different sources (datastream and file
system format) which makes using a single pkgtool variable difficult.
Also, SYSV packages in datastream format don't necessarily have uniform
names.  Therefore, use the existing 'simplename' attribute to specify
the datastream file name.
I tried something like this:

    def Install(self, packages, states):
        modified_packages = []
        for pkg in packages:
            pkg = self.pkgmogrify(pkg)
            modified_packages.append(pkg)
        return super(SYSV, self).Install(modified_packages, states)

but couldn't figure out how to avoid an ugly stack trace on an uninstallable package (one that requires interaction, like SUNWsneep).  Avoiding the single-pass install did the trick, but there's almost certainly some better way.