Fix for views showing errors in Editor

On certain machines, it appears that System.Core is loaded incorrectly
(perhaps wrong version?) and it causes Visual Studio to display cryptic error
messages in views such as for using ViewBag (`One or more types required to
compile a dynamic expression cannot be found. Are you missing a reference?`)
or failure for @Html.TextBoxFor ... to correctly deduce the type of `model`.

Explicitly specifying the assembly to use in Web.config appears to fix the issue.