Adding New Table by not touching the core of nopCommerce.

I want to add a new table in my existing nopCommerce database and call in "AffiliateProducts"
with the following columns ProductId, AffiliateId
The goal is to assign a product(s) to an affiliate(s) as follows

ProductId     AffiliateId
--------------------------
101                 1
101                 2
201                 1
301                 3

Whenever customers land to my website with the Affiliate URL like http://www.bookstore.com/books/?AffiliateId=1
I want to load my store's products plus the affiliate products in this case products with id (101,102)

How to reach my goal by not touching the core classes?

If I make any changes to the core classes on nopCommerce data structure, there will be a challenge for updating to newer version of nopCommerce.
Should I create a new plug in?
Is there any sample for that?

Even if I create my own classes I will be needed to make changes on CatalogController that is responsible to load the products and categories to use my new plug-in methods and functions.
Like this one.

public ActionResult Category(int categoryId, CatalogPagingFilteringModel command)
{

...
...

  var products = _productService.SearchProducts(categoryIds, 0,
                _catalogSettings.IncludeFeaturedProductsInNormalLists ? null : (bool?)false,
                minPriceConverted, maxPriceConverted,
                0, string.Empty, false, false, _workContext.WorkingLanguage.Id, alreadyFilteredSpecOptionIds,
                (ProductSortingEnum)command.OrderBy, command.PageNumber - 1, command.PageSize,
                true, out filterableSpecificationAttributeOptionIds);
...
...
...
}

I need to change the method for seraching products and pass the AffiliateId and return my products and products related to AffiliateId.

Maybe you can do what you want with a fork in Codeplex. Check how this multi-store extension is built
Another way would be to use ACL on categories/products (coming in v2.7 at end of december) creating a customer role for each affiliate ("Affiliate1", ...) and assigning the role when customer gets into the store. Check:
https://www.nopcommerce.com/boards/t/19389/suggestions-for-acl-on-categoriesproductsmanufacturers-and-multi-stores.aspx