set system=>true on non human user accounts

This is important to avoid uid/gid conflicts with accounts created
with fixed uids in normal user range.

This patch won't break existing configs because it only influences the
uid generation on new user / group creation and has no impact on existing
resources.
tomcat::instance: add parameter for logs folder mode
Merge pull request #35 from ckaenzig/set-user-system-param

set system=>true on non human user accounts
Merge pull request #36 from ckaenzig/logs-dir-mode

tomcat::instance: add parameter for logs folder mode
Merge branch 'master' of https://github.com/camptocamp/puppet-tomcat