Use github redirect to avoid certificate issues.

Possibly fixes #1033.
Fix permissions with the indirect installer cache.
targets/*: Blacklist selected releases/distros.

We use exit status 99 to indicate that a given combination is
unsupported (so we can detect it in tests).
targets/lxde: Do not install network-manager

Affects mainly Debian wheezy/jessie: When the chroot is terminated,
network-manager is killed, which brings down the wifi connection.

Does not hurt to specify it on non-Debian.
chromium: Debian has no chromium package for ARM. Sorry.

Also fix Debian package name (chromium-browser is an alias
on wheezy only).
test/39-alltargets: Test if all targets can at least be installed.

*common is blacklisted, as well as a few other lucky few.
edit-chroot: sync filesystem after backup is completed

Make sure that the data is actually on the physical device.
Merge pull request #1036 from drinkcat/backup-sync

edit-chroot: sync filesystem after backup is completed
targets/kali: Mark relevant targets as unsupported (same as wheezy).
Fix issues with bad cache after failed installer downloads.
Fix after review.
test/alltargets: Move from 39 to x0, so we run it on demand only.
Merge pull request #1042 from drinkcat/alltargets

Test all targets on all releases
audio: Relax matching rules for sbc package on wheezy

Some mirrors escape `+` as `%2b` in the URL, which causes the
regex not to match. Relax the regex so that we do not match the
`+` (that was probably overcautious in the first place).

Fixes #1043.
Merge pull request #1044 from drinkcat/wheezy-sbc-relax-match

audio: Relax matching rules for sbc package on wheezy
indirect installer: Use curl instead of wget

wget 1.12 on Chromium OS < 5116 (R33) is buggy and not able to
fetch the latest installer.

Also, use direct URL as curl does not follow redirections.
Create kde-minimal target
indirect installer: Fix curl fetching

Add -L so that curl follows redirection. Also, increase maximum
download time to 5 minutes in case the crouton installer grows
in size, but keep a 60 seconds connect timeout.

Finally, add -# so that the user is informed of the download
progress (again, more useful if crouton ever becomes larger).

Tested on a very old x86-zgb image 4100.89.0: curl behaves correctly.
Add junk to crouton indirect installer to make it an octet_stream
Treat crouton installer as a text file in git.