#3 - Base test case for support for collections and maps

Base test cases for #3 - Ability to override List/Set/Map property.

As there are many cases functional testing all of them with nebula-test plugin would be an overkill. I left 2 simple cases and moved other to unit/integration tests. The implementation would probably require to extract a mechanism from `DotNotationWalkerOverrideStrategy` to determine a field type (also a generic type for collections - like `foo.class.declaredFields[0].getGenericType()`) and leave only base types for `ApacheCommonsTypeConverter`. Therefore I left test in a very generic form.

I am not also sure about the name. ComplexType can suggest that complex/custom type can be passed. Collections and Maps is an alternative.

Probably not all test cases should be supported - to make the implementation easier. Also there are for sure cases I missed.

Regarding `def` as extension is exposed API I would consider the lack of support for fields defined as `def` or use specific default behavior which to cover only base cases (the easier way).

If you decide to keep so many test cases the duplication in `where:` part could be eliminated with some Groovy tricks on `propertyName` column.
Was this supposed to use `ComplexTypeExtension`?