Support apt.postgresql.org version specific packages.

This change will allow to test beta and release candidate version of
postgres from apt.postgresql.org.

For stable version this change will make available the libpq package
for that specific version (that will not hurts).
Merge pull request #255 from mnencia/patch-6

Support apt.postgresql.org version specific packages.
Fix license file.
Merge pull request #258 from apenney/license

Fix license file.
Prepare 3.0.0 release.
Merge pull request #259 from apenney/300-release

Prepare 3.0.0 release.
Special case for $datadir on Amazon

Closes #252
Merge pull request #262 from bcomnes/amazon

Special case for $datadir on Amazon
Optionally manage postgresqld service

If you use PostgreSQL in a cluster environment like Pacemaker,
Puppet should not manage the service.
Additionally, PostgreSQL should not be started on boot in such
an environment.
It is still possible to manage pg_hba rules etc.
The reload manifest remains unchanged, a reload is usually
safe in a cluster environment.
Update server_spec to include optional service management