Basic integration of the lazy initialisation functionality.
Minor changes.

* Added file header comment to `SetterMethodChecker.java`.
* Extended `SetterMethodCheckerTest.java` by test cases for Lazy
  Initialisation.
* Changed `MutatesAsInternalCaching.java` to be effective immutable
  as using Lazy Initialisation.
Merge jufickel's pull request #42
Partially migrate to jufickel's advanced lazy initialisation algorithm. Add a temporary option to retain the old algorithm while we iron out the curves.