Add collectd support.

Include openvpn and write_graphite plugins.
Add collectd df plugin support
Add Solaris collectd parameters
Fix collectd service subscription to conf file.
Add disk plugin to collectd.
Add mysql plugin to collectd.
Template openvpn plugin and parameterize the class
Change include plugin file to include conf.d

Removing includes for each plugin and instead
including a conf.d directory.
Add collectd::plugin define for unconfigured plugins
Fix plugins with wrong metaparams
Add ensure option for collectd::plugin
Add smoke tests
Add syslog plugin
Add purge option to collectd class
Add purge_config option to collectd class
Fix bug in collectd::plugin define
Remove unneeded quotes on certain plugins
Rename collectd.d to conf.d for easier tab completion
syslog plugin test loglevel should be log_level
Add missing quotes to openvpn plugin