Simplify the createComponents() methods.

- Make stored fields non-stored, if they don't have to be stored. This
  allows us to specify a reader when adding the field, rather than
  providing a dummy value and put logic in createComponents() to pass
  the reader to the tokenizer.

- Override TokenStream.reset() in the tokenizers so that the
  createComponents() methods don't need custom sub-classes of
  TokenStreamComponents in order to reset the tokenizers.