Added new script to install packages required by the
test suite, and added step in instructions to call it.
For now, it just ensures that rsync is installed, as
that's needed for the test suite itself to work.
The install_sdp.sh script itself installs everything
it needs, and in fact one of the tests uninstalls
rsync just to ensure the install_sdp.sh script handles
that well (which an earlier version didn't).