Expand EditModuleBase to handle situations when itemId is sufficient to identity an item, but it is not PK

[roman-yagodin]

Code to review:

• https://github.com/volgau/R7.Dnn.UserHtml/blob/master/R7.Dnn.UserHtml/EditUserHtml.ascx.cs
• https://github.com/roman-yagodin/R7.University/blob/master/R7.University.EduProgramProfiles/EditContingent.ascx.cs#L185-L194