#207 adder method for collections on target

For review, it is not yet completely finished. It contains TODO's in the `MapperCreationProcessor.java` and `Type.java`. It also lacks more unit test (placeholders are in place).
Out if interest, what is the reason for using this `init()` method (and creating an anonymous class) instead of just `Arrays#asList()`:

    private static final List<ReplaceRule> SINGULAR_DALI_RULES = Arrays.asList(
        new ReplaceRule( "(us|ss)$", "$1" ),
        new ReplaceRule( "(ch|s)es$", "$1" ),
        new ReplaceRule( "([^aeiouy])ies$", "$1y" ),
        new ReplaceRule( "s$", "" )
   );

Btw. I think we should extract all that singularization/pluralization stuff into a separate class.