Optionally manage postgresqld service

When using a cluster resource manager (CRM) such as Pacemaker to manage
a Postgres failover/HA cluster, the CRM should have authority over
starting and stopping the service, not Puppet. The new parameter
'manage_service' allows for that. This is implemented exactly like in
the puppetlabs-mysql module.
Set /tmp as default CWD for postgresql_psql

This has been discussed in issue #148. The postgresql_psql type doesn't
change the CWD to something safe when running psql as the postgres user.
During a regular puppet run the CWD remains "/root", to which the
postgres user usually does not have access, resulting in failed psql
calls and failed puppet runs. This simple change makes "/tmp" the
default CWD for postgresql_psql.
Merge branch 'master', remote-tracking branch 'remotes/origin/psql_cwd'
Merge branch 'master', remote-tracking branch 'remotes/origin/manage_service'