Added additional tests for map classes based on mutation results

[adwiii]

I used this project as a learning tool for getting familiar with Pitest mutation testing and picked a few test classes to improve based on the result. I picked the below classes because the current test suite provides 100% line coverage, but PIT found surviving mutants.

Transformed Map

In the TransformedMapTest class, the testFactory_decorateTransform method did not provide a key transformer. In TransformedMap::transformedMap the call to decorated.clear() is only necessary if the key transformer changes the key set. This adds a test with a key transformer.

Lazy Sorted Map and Predicated Map

Both LazySortedMap and PredicatedMap have tests that check if the comparator is null, but never check for a non-null value. The added tests check that if a non-null comparator is used then it is properly returned.