[SPARK-7985] [ML] [MLlib] [Docs] Remove "fittingParamMap" references. Updating ML Doc "Estimator, Transformer, and Param" examples.

Updating ML Doc's *"Estimator, Transformer, and Param"* example to use `model.extractParamMap` instead of `model.fittingParamMap`, which no longer exists.

mengxr, I believe this addresses (part of) the *update documentation* TODO list item from [PR 5820](https://github.com/apache/spark/pull/5820).

Author: Mike Dusenberry <dusenberrymw@gmail.com>

Closes #6514 from dusenberrymw/Fix_ML_Doc_Estimator_Transformer_Param_Example and squashes the following commits:

6366e1f [Mike Dusenberry] Updating instances of model.extractParamMap to model.parent.extractParamMap, since the Params of the parent Estimator could possibly differ from thos of the Model.
d850e0e [Mike Dusenberry] Removing all references to "fittingParamMap" throughout Spark, since it has been removed.
0480304 [Mike Dusenberry] Updating the ML Doc "Estimator, Transformer, and Param" Java example to use model.extractParamMap() instead of model.fittingParamMap(), which no longer exists.
7d34939 [Mike Dusenberry] Updating ML Doc "Estimator, Transformer, and Param" example to use model.extractParamMap instead of model.fittingParamMap, which no longer exists.