ubuntu/bootstrap: Fix debootstrap download fallback.

Now it's a .tar.xz file, instead of .tar.gz. Should fix #740.
Merge pull request #742 from drinkcat/debootstrap-xz

ubuntu/bootstrap: Fix debootstrap download fallback.
croutonxinitrc-wrapper: Maximize Xephyr on startup

Recent versions of Xephyr (>=1.15) do not start in full screen:
tell croutonwmtools to maximize it.

Fixes #744.
croutonxinitrc-wrapper: Update comment.

Indicate which versions of Xephyr are affected, so that the hack
can be removed later on.
croutonxinitrc-wrapper: Make sure xbindkeys is killed on exit.

Steps to reproduce:
 - enter-chroot in a first crosh
 - startxfce4 in a second crosh, then press Ctrl-C

ps -eaf shows that xbindkeys is still running. However, its parent
is now PID 1, and it received a SIGHUP (due to the parent shell
process terminating). Unfortunately, xbindkeys does not handle
SIGHUP correctly, and hangs forever (locked in a futex call
according to ptrace: did not investigate further), and does not
process any further key presses.

This might explain #754, and some similar bugs reported on Google+.
Merge pull request #759 from drinkcat/xbindkeys-forcekill

croutonxinitrc-wrapper: Make sure xbindkeys is killed on exit.
Merge pull request #750 from drinkcat/xephyr-fullscreen

croutonxinitrc-wrapper: Maximize Xephyr on startup
add Xsession script to launch Unity indicators
CD to a known directory before starting the test.

Fixes some failures when the daemon is run from transient directories.
use XDG autostart instead of Xsession
unconditionally run croutonversion to get RELEASE
moar unity
Merge branch 'unity-trusty' of https://github.com/smibarber/crouton
Ubantoo 14.04 Trusty Trilobite in, 12.10 Quantal Quagga out.
Add desktop distribution targets.

Dedicated to people who love full environments and hate disk space.
Let the desktop targets bring in whichever browser they please.