Add a ProductRepository and failing tests
PASS: Building a query for a single entity

Note that this tests passes while the materialization tests fail
because this test doesn't actually execute the query.

When someone queries our ProductRepository, we ferry the request
to the underlying DataServiceContext.
PASS: Executing a query

By adding a property onto the Product and ignoring any missing
properties on our POCOs, we can actually execute the queries.

The POCO we're using as our entity must provide at least one property.
PASS: Querying a result set with multiple items
Merge branch 'product-repository'