apt::force: Added 2 parameters for automatic configuration file handling...

...; fixes #modules-1306

when updating or installing newer packages with apt::force and you have changed previous
configuration files aptitude or apt-get will prompt what to do. You can suppress that
by pre-define the action with cfg_files parameter (new, old or unchanged and its backward
compatible if not defined). With a second optional parameter cfg_missing you can force
your provider to install missing configuration files as well.

Signed-off-by: Martin Seener <martin@seener.de>

apt::force: Changed selectors used in force.pp to case statements; refs #module-1306

Signed-off-by: Martin Seener <martin@seener.de>

apt::force: rspec: fixed the failing tests and added validate_re for cfg_files and validate_bool for cfg_missing. Also removed default values for both case statements and only allow pre-defined values or true/false. Furthermore enhanced the README refs #module-1306

Was able to fix the failing rspec tests for the patch.
Thanks to Morgan Haskel.

Signed-off-by: Martin Seener <martin@seener.de>

Despite the puppetlabs-stdlib documentation says validation_re supports 3 arguments the tests failed telling that only 2 are supported. Fixed this by removing the 3 optional argument; refs #modules-1306

Signed-off-by: Martin Seener <martin.seener@barzahlen.de>

apt::force: updated readme refs #module-1306

Signed-off-by: Martin Seener <martin@seener.de>