Add switch to configure database SSL connection

Hi,

this patch adds a switch, to optionally use SSL for PostgreSQL database connections. This adds only the switch, setting up the appropriate trust- and keystores has to be done outside of this module (e.g. puppetlabs-java_ks).
By default, all database connections will be without SSL.
I have disabled the database connection validation, if SSL is enabled. The psql command expects the certificates in the .postgresql folder of the executing user. Otherwise you would have to store the certificates multiple times on the machine.

Regards,
Stefan