Skipping of unchanged scenarios is now based on MD5-sums of all classes

Skipping of unchanged scenarios is now based on MD5-sums of all classes

When working with Netbeans, the schema was often rebuild without need.
The cause of this behaviour was, that Netbeans (or Maven itself) sometimes
touches unchanged classes. To avoid this, hibernat4-maven-plugin now
calculates MD5-sums for all annotated classes and compares these instead of
the last-modified value.