Improve OS-related params

This patch tries improve params detection based on $::operatingsystem : 

- "doc_package" is quite os-dependant, puppetdoc beeing provided by the perl package in RHEL/CentOS flavours, perl-doc in Debian & derivates

- "Automatic" package naming is also tied to the OS : RHEL/CentOS flavours are often naming packages perl-<module_name> but Debian & friends are naming them lib<module_name>-perl (thus adding the "$package_suffix" variable".

Default values have been kept.