Stop using config_file from the common module

This define doesn't add much of a shortcut and imposes a dependency on
the "common" module. We'll be better off with the small repetition but
less tightly coupled modules.

Sadly, the "common" module is still required, but that is going to be
the focus of the commit that follows this one.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>
Make apt::preferences_snippet place files in /etc/apt/preferences.d

Since Debian Squeeze, apt supports a .d directory for preferences
(pinning). Simplify management by just placing files inside this .d
directory.

This removes the need for concat and concat::fragment resources, so
removes the dependency on the concat module. It also removes the need
for a moduledir that was needed for the concat module magic, so we also
get rid of the dependency on the common module.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>
Some stylistic corrections in manifest examples in the README

Signed-off-by: Gabriel Filion <lelutin@gmail.com>
Define an alias when enforcing absence of /etc/apt/preferences

This ensures that resources that set a dependecy on the
"File['apt_config']" file, as mentioned in the README, can always
resolve.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>
Precision on file name format in preferences.d directory

Signed-off-by: Gabriel Filion <lelutin@gmail.com>
Merge branch 'master' into issue_3953