ShadowString, ShadowThread: add constructors for un-initialized shadows.
StringInfoHandler, ThreadInfoHandler: let ShadowObjectTable handle the registration, keep only IO in the handler code.
ShadowObjectTable: drop the debug parameter from the register() method, use logging instead.
ShadowObjectTable: use special constructors when creating un-initialized shadows of special objects.
ShadowClassTable: avoid using the debug parameter when calling the register() static method.