Improve build

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>
ks: Improve package selection

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>
spec: Add some descriptions

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>
imgbase: Make hooks more specific

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>
imgbase: Improve hook documentation

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>