Made datadir and confdir configurable in ::params for the whole module

You can now supply datadir and/or confdir in ::params like so

    class { 'postgresql::params':
        version => $psql_version,
        manage_package_repo => true,
        datadir_custom => "/postgres/pgsql/${psql_version}/data",
        confdir_custom => "/postgres/pgsql/${psql_version}/data"
    }
   Class['postgresql::params'] -> Class['postgresql::server']

You also want to leave out ::config::pg_hba_conf_path and ::config::postgresql_conf_path as they are derived from ::params anyways. 
I left those parameters in to not break code that relies on them. Should be removed in the future tho.