Tweak factory function parameters and scope

* Modified the factory functions to be executed in the instance context
  (instead of passing the instance as the first parameter).
* When called on an instance during construction in coordination with
  automatic injection by Deft.mixin.Injectable - the constructor
  arguments are passed as parameters.
* When called on an existing instance with manual injection via
  Deft.Injector.inject() - the initial config is passed as the only
  parameter.