Clarify the Serialization Consideration chapter

[jerrinot]

For example it says: "Register the serializers for nested objects". It should show how to do it.
Also this part is not clear to me: "Regarding arrays in a serializable object, you can use methods like writeIntArray if the array is of a primitive type." What's so special about arrays? Is this related to customer serializers?

[mustafaiman]

@jerrinot can you take a look at #278 and see if it looks better that way?

[furkansenharputlu]

@jerrinot It seems this issue is resolved through #340. Wdyt ?

[jerrinot]

very nice, @furkansenharputlu: well done!