Rationale: backports.org's iceweasel is too buggy. Squeeze's AdBlock-Plus is not
compatible with Lenny's iceweasel.

This reverts the following commits, and adapts the resulting tree to be
consistent with current state:

 3a3f9ade
 bfe2ab60
 7c01ee86

The Debian packaged adblock-plus extension is not compatible with older
Lenny's iceweasel. Stopped installing iceweasel-gnome-support, which does not
exist in Squeeze anymore, and whose backport is not installable.

Leave .list at the end of our always-enabled packages list (amnesia-common),
remove it from others, and copy at lh_config time the needed additional
packages lists to .list-named ones to enable them.

- packages lists must now be named *.list
- the scripts/ directory has been renamed to auto/

/home/amnesia is missing, as no clean way to include it is implemented yet.