Changed the implementation of DatabaseSchema.EntityClass and .ImplicitEntityClass to computed properties instead of fields that need to be assigned.
Made weaver schema DatabaseClass expose IsImplicitEntityClass and IsEntityClass internally, rather than keeping them private. We'll make use of these in the code host loader.
Made sure all properties defined as part of EntityWeaving was set as public by default.
Changed the code host loader not to generate either TypeDef or TableDef instances for the implicit Entity type.