Manage Piwik and dependencies

Manage the Piwik analytics software and its dependencies.  This includes
MySQL and PHP
Fix hiera key name for piwik mysql password
Fix mysql::db type name
Fix php-fpm in piwik profile
Declare piwik class via fully qualified name
Only manage php-mysql once
Resolve username and service name
Manage PHP manually for now
Install piwik with staging module
Fix user param for staging::deploy
Add piwik nginx vhost
Add creates param to piwik staging
Change php-fpm port for piwik
Add php-mbstring to pwik profile
Install php-xml