Move all Initscripts of the system, into an extra directory

Move all Initscripts of the system, into an extra directory

Till now all init scripts going into src/initscripts/init.d so they are
installed by the lfs file initscripts. Because of that they also appear
in the rootfile of the "package" initscripts.

This has some disadvantages:
- the initscripts of the packages appear in the 3 rootfiles (one for
each arch) which are annoying because for every package with an
initscript 4 rootfiles (the 3 of the initscript package + the rootfile
of the package) are important.
- The rootfiles for a package are installed by lfs/initscripts but this
should happen only in the build of the package

To solve this issues all rootfiles for the core system are moved into
src/initscripts/init.d/common. Only the initscript in this directory are
installed by lfs/initscripts. So all initscripts for packages are
located in src/initscripts/init.d and are not installed by
lfs/initscripts.
So only the initscripts of the system appear in the 3 rootfiles of the
initscripts package. The initscript of a package appear only in the
rootfile of the package. This makes the maintaining of initscript
easier.

Signed-off-by: Jonatan Schlag <jonatan.schlag@ipfire.org>