Drop remastersys for debootstrap + fakechroot

remastersys is no longer required to create an ISO, instead debootstrap creates
the basic environment, then fakechroot and fakeroot are used to install
packages and copy files.

Overview of the new process:
 1. install.sh is called by the user, with a path to the work directory
 2. fakechroot + fakeroot are used to invoke install.sh again, --second-stage
   1. debootstrap runs, creating a base environment in $workdir/chroot
   2. chroot is used to invoke install.sh inside the chroot, --third-stage
     1. packages and Karoshi files are installed as before
   3. final cleanup occurs
   4. filesystem.squashfs is generated, followed by the ISO itself

pre-commands and post-commands have been replaced with hooks, defined in
install/hook. See install.sh for details

Other changes:
 - the 'administrator' user has been replaced by a 'karoshi' user
 - new PPAs with updated software are configured:
   * Gimp PPA
   * LibreOffice PPA
   * MariaDB PPA
   * VirtualBox PPA
   * WebUpd8 PPA
   * Wine PPA
 - a new utility, cleanup.sh, is available
   * this library provides cleanup and error handling functionality to any
     scripts that source it. it could be used heavily in place of exitfunc
     in set-network (see #69)
 - ifconfig dependency has been completely dropped
   * as much as possible, /sys/class/net is used to gather information
 - the installer now uses a background
Karoshi Client translation support, fixes #23

l10n/update.sh generates l10n/karoshi-client.pot and all supported
language .po files. l10n/gtranslate.sh can run these files through Google
Translate, or the .po files can be translated by a human.

On installation, the .po files are converted into .mo files and put into the
correct places.

Ubiquity language selection and/or preseed will set the system locale
Remove Manage Flags .desktop

GUI mode was removed in 33345eeade2c05ae3f12d8aba617a3787dfa44ce
Desktop file translation support, fixes #70
[l10n] Google translations
Merge pull request #79 from the-linux-schools-project/l10n

l10n support, replace remastersys with fakechroot system