Change xinetd submodule to puppetlabs-xinetd
Add database management support

Adding the puppet-postgresql, puppetlabs-mysql, stdlib and concat modules.
The existing concat module is renamed to prevent a conflict and since it's
types/providers, the name doesn't matter.

Clarifying the licensing statement as these are Apache 2 licensed modules.
Version bump
Add database options to generate_answers
Add stable release info, remove old submodule URLs
Fixes #2442 - Write the answers file _before_ running puppet