- spec: fix dependencies for mini variants
Make sure that all mini variants won't be installed in real systems and won't
be involved when building medias with kiwi. Note that sub-packages that
requires systemd (such as udev) don't need any special treatment since the
specific deps are inherited from the main (mini) package.
- spec: simplify systemd-mini-doc dependencies by assuming that the doc
sub-package can't be a build requirement for other packages.
- spec: libsystemd-mini and libudev-mini need to provide libsystemd and libudev
respectively

- Rename systemd-sysvinit into systemd-sysvcompat
systemd-sysvinit was probably provided to allow systems to switch from
sysvinit to systemd by overwriting /sbin/init with a link to systemd. But this
isn't very useful anymore due to the fact that sysvinit is not supported since
several years. Therefore the subpackage contains now the files needed to keep
backward compatibility with SysV init scripts (most notably sysv-generator)
and has been renamed accordingly. The few files that are not specific to
sysvinit (such as /bin/init) have been moved to the main package.
Normally this new subpackage shouldn't be needed (since all packages use
systemd unit files) unless a 3rd party application is installed and still
relies on SysV init scripts.

- systemd.spec: explicitely turn on/off build options
Hence a feature can't be accidentally turned on/off because its dep is pulled
in or removed due to another feature being turned on/off.