Add module config

Modules might need to have custom options. This creates the file on `mods-available` and symlinks them to `conf.d`, both at `/etc/php5`.

## To dos
- support 5.3
We can profit over paths in variables, like:

- `/etc/php5/mods-available`
- `/etc/php5/conf.d`

I already have a number of variables for paths following the name convention: `hwr_path_php_<what>`, I suggest the following names:

- `/etc/php5/mods-available`: `hwr_path_php_mods_available`
- `/etc/php5/conf.d`: `hwr_path_php_mods_enabled`

These variables should be defined under `vars/Debian.yml`.