* Support version selection for database plugins
* Don't consider unversioned plugins for version selection algorithm
* Added version to 'plugin not found' error
* Add PluginFactoryVersion function to avoid changing sdk/ API
This is part 1 of 4 for renaming the `newdbplugin` package. This copies the existing package to the new location but keeps the current one in place so we can migrate the existing references over more easily.
