Set up Unicode/UTF8 and console fonts via console-setup

Set up Unicode/UTF8 and console fonts via console-setup

Our old approach with running loadkeys, setting console font and
invoking unicode_start via grml-autoconfig is incomplete for nowadays'
environments.

We tried to fix that by changing the order in which we set up the fonts,
runnning loadkeys and finally invoking unicode_start via grml-autoconfig
(see: grml/grml-autoconfig@c820a66). But this changed only the behavior
on tty1, the other consoles still had problems when trying to display
unicode characters (see e.g. `systemctl status` output).

The proper solution is to configure /etc/default/console-setup as needed
(doing this with this change) and rely on console-setup afterwards to do the right
thing (implemented within grml-autoconfig).

With this change we ship a default /etc/default/console-setup via
GRMLBASE, which can be customized as needed by users of grml-live
through separate FAI class files.

Explicitely added console-setup to GRMLBASE since we rely on it
nowadays.

Thanks: Michael Schierl (@schierlm) + @qlplq for feedback and Darshaka Pathirana for debugging this and providing a preliminary PR
Closes: grml/grml-autoconfig#9, grml/grml#50
Relates to: grml/grml#101