Update Mapper generation to use factories

[sav007]

Sorry for such big PR but that because changes touch all test fixtures.

PR changes the way how ResponseFieldMapper been generated to accept factory to instantiate the models.

This class FragmentsResponseMapperBuilder responsible for Mapper generation of Fragments class
This class SchemaTypeResponseMapperBuilder responsible for Mapper generation for the rest schema object types.

Example of generated class with mappers

Example how to register Mapper in retrofit converter for POJO classes

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(server.url("/"))
        .addConverterFactory(new ApolloConverterFactory.Builder()
            .withResponseFieldMapper(AllPlanets.Data.class, new AllPlanets.Data.Mapper(AllPlanets.Data.FACTORY))
            .withResponseFieldMapper(ProductsWithDate.Data.class, new ProductsWithDate.Data.Mapper(ProductsWithDate
                .Data.FACTORY))

Closes #142

[digitalbuddha]

lgtm