l10n support, replace remastersys with fakechroot system

Mega PR.

Build process changes:

 * Remastersys is no longer used to create ISOs, instead fakeroot + fakechroot are used
 * 'administrator' has been replaced with 'karoshi'
 * Updated PPAs are used for Gimp, LibreOffice, MariaDB, VirtualBox, WebUpd8 and Wine
 * Introduction of `cleanup.sh`, a Bash library to handle errors and clean up
 * Installer background
 * `ifconfig` dependency is completely dropped

l10n changes:

 * All script strings and relevant .desktop files are translated
 * `l10n/update.sh` extracts strings from scripts and .desktop files, generating a PO template and the supported language PO translation files
 * `l10n/gtranslate.sh` runs the PO files through Google Translate

Miscellaneous changes:

 * The Manage Flags administration .desktop file has been removed