add parameter "version" to postgresql::server::extension to update the extension version

When an extension package is updated, this does not automatically change the effective version in each database.
The SQL command ALTER EXTENSION... must be executed on a per-database basis to complete the update of the extension.

This pull request adds the parameter "version" to postgresql::server::extension

When version is specified (can be latest ) the ALTER EXTENSION is applied to the database.

https://github.com/puppetlabs/puppetlabs-postgresql/pull/896