Fix IPv4 address validation in next_server field in profile/system
Rename ks_mirror directory

ks_mirror contains installation tree of Linux distributions.
distro_mirror reflects directory purpose much better.
Rename 'kickstart' to 'automatic installation'

Cobbler already supports autoyasts and preseeds, automatic
installation file terminology should reflect that. This makes
Cobbler more generic.

Also, discard /var/lib/cobbler prefix in autoinstall templates
and autoinstall snippets in web UI and recursively search
for autoinstall templates in its directory.
Merge pull request #1284 from alanoe/alanoe/rename_kickstart2

alanoe/rename kickstart2