CLOUDSTACK-7143: upgrade systemvm to latest debian stable, 7.6.0.
CLOUDSTACK-7143: split base.sh into its two functions.
CLOUDSTACK-7143: move network tuning from cleanup.sh to its own script.
CLOUDSTACK-7143: merge systemvm templates, step 1: remove differences
CLOUDSTACK-7143: merge systemvm templates, step 2: only one template remains
CLOUDSTACK-7143: remove 'manual' from preseed config. No other changes.
CLOUDSTACK-7143: reformat definition.rb code. No other changes.
CLOUDSTACK-7143: move add_backports to apt_upgrade.sh
CLOUDSTACK-7143: cleanup apt_upgrade.sh code
CLOUDSTACK-7143: add vagrant_box_build_time file that's standard with current veewee templates
CLOUDSTACK-7143: cleanup configure_gruh.sh code

Adding a check whether GRUB_TIMEOUT has already been set, and if it has,
skip re-running update-grub.
CLOUDSTACK-7143: split login config out from postinstall.sh
CLOUDSTACK-7143: cleanup configure_login.sh code

Had to change various things to make this code re-entrant. In particular,
the sed-based manipulation of /etc/sudoers is gone and replaced with a
simpler, minimal (but compatible) sudoers file.

Remove the sshd_config tuning since sshd_config is overwritten when we
apply the cloud_scripts overlay (from build.sh).
CLOUDSTACK-7143: split locale config into its own file
CLOUDSTACK-7143: cleanup configure_locale.sh code
CLOUDSTACK-7143: move fix_acpid to its own file
CLOUDSTACK-7143: cleanup configure_acpid.sh code
CLOUDSTACK-7143: cleanup cleanup.sh code
CLOUDSTACK-7143: split connection tracking config into its own file
CLOUDSTACK-7143: move networking logic from postinstall.sh to configure_networking.sh