Added new class SetValueCallbackInvoke to Starcounter (namespace Starcounter.Internal) that will act as the facade for the weaver when emitting code that are to invoke callbacks of ISetValueCallback.
Added helper method SetValueCallbackInvoke.AttributeIndexToColumName, that are to be used to translate indexes to their corresponding column name (which is what we want to pass to ISetValueCallback).
Redesigned the ISetValueCallback interface according to the second option ("2. Switch to one method per data type") in this comment: https://github.com/Starcounter/Starcounter/issues/2420#issuecomment-63812826.
Made all SetValueCallbackInvoke invoke their corresponding target method in the new ISetValueCallback interface, after first doing the necessary column name lookup.
Removed obsolete methods in ISetValueCallback and DbState that implemented first version of the set value callback mechanism.
Extended the internal weaver class DbStateMethodProvider to support additional lookup of SetValueCallback invocation entrypoint methods and cache these while doing lookup of the basic DbState methods.
Extended the API of the weaver DbStateMethodProvider class to return an optional SetValueCallback infrastructure method reference to the weaver when asking for the Set accessor method (GetSetMethod).
Adapted the weaver transformation component to recent changes in ISetValueCallback and the intrastructure SetValueCallbackInvoke class the weaver emit calls into.