Switched to RazorGenerator ViewEngine

This is essentially a total revamp of the code, based on Zack's original
idea.  The revamp includes upgrades to MVC4, latest StructureMap
release, etc.  Most importantly is the switch to Razor view files
(specifically using RazorGenerator).

Additionally, I extended the potential for customization by Tenant by
passing the object to the Controller as well as each View.

Also, I switched from "EnabledFeatures" model to "DisabledFeatures"
model for feature control by tenant.  All features default as enabled,
but can be turned off for a given tenant.