Switch to metadata.json for Puppet forge releases

Since puppet 3.x, Puppet Labs Forge accept only the metadata.json file
for module description (Modulefile is now deprecated). This patch
convert the Modulefile to metadata.json, and update module namespace for
a future release (on Stackforge).

Change-Id: I57405d740660adcbbb007aeb35dca1f8dcc4a9cc