Fixed "Casting to Decimal is not supported..."

Fixed error "Casting to Decimal is not supported in LINQ to Entities
queries, because the required precision and scale information cannot be
inferred."

Solution was not to cast, but to -truncate- through integer conversion
and then cast to decimal. In other words, use
(((decimal)((int)(x.Discount * 100))) / 100)
instead of
(decimal)x.Discount

It produces terrible SQL, like this:
( CAST(  CAST( [Extent4].[Discount] * cast(100 as real) AS int) AS
decimal(19,0)) / cast(100 as decimal(18)))
Cleaned code, documented key LINQ reporting items

Also applied LINQ fixes to the other report, GetCustomerOrderSummaries()