Install spice tools for Debian/Ubuntu distros too

[ugjka]

data/install-script has Fedora install these tools but they're not installed for other distros:

xorg-x11-drv-qxl
spice-vdagent
spice-webdavd
qemu-guest-agent

For Debian and Ubuntu the equivalents are:

qemu-guest-agent
spice-vdagent
xserver-xorg-video-qxl

All 3 are available in all supported Debian and Ubuntu releases. One thing to look out for is that 2 of those packages are in Ubuntu's universe repository which might not be enabled by default during a basic Ubuntu install.