Enforce ulimits

Enforces the limits set in /etc/security/limits.conf by including pam_limits.so in common-session and common-session-noninteractive.

common-session-noninteractive is relatively new and was not managed by Puppet previously, so I have added it here using defaults from Ubuntu Precise with the addition of pam_limits.so and pam_loginuid.so.

Tested on Precise and Lucid:

```
root@vm:~# sudo -u deploy bash -c 'ulimit -n; ulimit -u'
16384
512
```