Add support for Zend\Db for those trying to modernise their ZF1 deployments.
The plugin must be added with registerPlugin() and takes two parameters: adapter and backtrace. Adapter is an instance of Zend\Db\Adapter\AdapterInterface and backtrace is a boolean whether to include the call stack to the query.
This release also removes the deprecated Constants plugin (superseded by Variables) and cleans up the code a bit.