Fix smbfs example in fstab

mount.smbfs is apparently gone, and mount.cifs doesn't understand "defaults" any more.
Switch default filesystem from ext3 to ext4

It should be safe to default to ext4 nowadays with Debian/wheezy
being the stable Debian release.
Provide --debug option for very verbose execution

This effectively executes grml-debootstrap under 'set -x'
(including the chroot script), so it's easy to generate an
execution log via e.g.:

  grml-debootstrap ... --debug --force 2>&1 | tee -a grml-deboootstrap.log

and providing it to grml-debootstrap developers for further
investigation.
Support execution of --grub when installing to target directory

Thanks: Michael Renner <michael.renner@amd.co.at> for initial bug report and sponsoring my development time
Copy /etc/network/interfaces from host system, unless --nointerfaces is used or target is a VM

Thanks: Michael Renner <michael.renner@amd.co.at> for feature request and sponsoring my development time
Update documentation WRT supported releases and some minor fixes
Clarify usage of default hostname ($HOSTNAME is considered)
Support --nokernel option to skip installation of default kernel images

As needed in a $customer environment (not to be named [yet]).
Do not enable security mirror for lenny release, being unavailable/unsupported nowadays
Release new version 0.63
Initial README.md (esp. for Github users)
Set up default /etc/network/interfaces with dhcp for eth0 in VM use case

Network interfaces in VM should listen to DHCP by default,
and if /etc/network/interfaces doesn't exist at all (so
takeover from host to guest isn't possible either) create
a sane default as well.

Thanks: Christian Hofstaedtler <christian@hofstaedtler.name> for suggestion + review
Thanks: Ulrich Dangel <mru@spamt.net> for review
Fixes #20
Provide option --defaultinterfaces to install default /etc/network/interfaces

This should complete all combinations that make sense WRT
default /etc/network/interfaces handling
Release new version 0.64
Add option --vm to install VMs into LVs and such

--vmfile insists on creating an image using qemu-img, whereas --vm
requires an existing container (for example an LVM LV).