add usecase examples

doc/tutorial/auto_examples/usecase/sg_execution_times.rst

doc/tutorial/auto_examples/usecase/usecase_function.ipynb

doc/tutorial/auto_examples/usecase/usecase_function.py

doc/tutorial/auto_examples/usecase/usecase_function.rst

...ial/auto_examples/usecase/usecase_function_codeobj.pickle

...s/multimodal.kernels.lpMKL.MKL.decision_function.examples

...s/multimodal.kernels.mvml.MVML.decision_function.examples

doc/tutorial/times.rst

examples/usecase/__init__.py

examples/usecase/plot_usecase_exampleMKL.py

examples/usecase/plot_usecase_exampleMVML.py

examples/usecase/plot_usecase_exampleMuCuBo.py

examples/usecase/plot_usecase_exampleMumBo.py

examples/usecase/usecase_function.py