Anaconda no longer includes the liveinst script in the core package.
This means the live iso will just be a live desktop, not a live
installer.
Resolves: rhbz#1876563
Anaconda has moved some of the live related requirements into a new
package, anaconda-live, which needs to be included in the kickstart.
Related: rhbz#1691319
Also add comments to the top of the example kickstarts describing how
they are meant to be used and providing an example cmdline. In some
cases, like rhel-minimal.ks, it can also be used for a live-iso but
requires a couple of extra packages for that to work.
Resolves: rhbz#1730937
