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 believe that the file is deleted when it is no longer referenced, just like the self.noaskfile  - the purpose of the self.tempfiles is to hold that reference. I'll double check this.