Added a new SpringPackageScanningConfigurator

The new configurator uses the URL prefix: `spring-package-scanning` after which the packages can be specified in a comma-seperated list.
Furthermore, the dialect must be specified as a `dialect` property.

Example: `spring-package-scanning:com.example.auction?dialect=org.hibernate.dialect.HSQLDialect`

With this configurator no mapping files are necassary.