LBFGS optimier and new test cases for Poisson and Gamma regression

* Add LBFGS optimizer to both Poisson and Gamma regression models.
* Add real-world data set to the test suites. 
* Modify the ``generatePoissonInput()’’ method in test suite to generate multi-dimensional test data.


Right. My opinion is that we keep this parameter, and use L2 regularization. Which regularization to use depends on the data set. In out test suite, L2 is preferable to L1 for the low-dimensional test data.