...to setup kms/xorg videodrivers for installer.

basesystem

- ported from m-p-d;
- generalized mediawiki, use/volumes/cliff-server;
- added centaurus/disk;
- dropped ganeti (no more in p9);
- x86 builds (both of them);
- e2k builds (ditto).

This works around DRI3 problems resulting in caja getting
BadWindow with panel applets subsequently failing to jump
into dock (which doesn't exist just yet):

* setup-libgl-dri3-disable tunes libGL to avoid DRI3,
* setup-mate-nocomposite asks MATE to avoid compositing.
Suggested-by: Denis Medvedev <nbr@altlinux.org>

PS: added setup-mate-terminal while at that to work around
the weird theming problem resulting in dark gray on black
colour scheme in Terminal; note that there's a fork here:
pkg.in/lists/workstation/mate (wasn't avoidable easily
at the moment).

These have been:
- taken from x86_64 server iso (in substituted form);
- checked against m-p-d where needed;
- renamed from centaurus-* to centaurus/*;
- updated with s/samba-server/samba/;
- archdep bits adjusted for m-p-d/m-p syntax difference;
- amended with some tester feedback based additions included;
- pruned regarding p9/branch packages availability.

Use some installer-features in vm/*.

For video conferences.
Suggested by aen@.