Ls addsampler fix

Finally completed the integration of the sampler inside the generation process. Now, the generation of the sets of designs uses a proper samples, where different strategies are integrated. Therefore, the main changes be listed as:

• Integration of sampler, now with "sampling" (KDE) and "bayesian" strategies.
• Writing the docstrings of all the files modified here
• Improve the speed of the "sampling" strategy, by removing the steps of update the engine, as it is not possible here
• Change the name of the aaad/generation to aaad/sampler, as it is less confusing
• Clean a file, and a few other small things

Even though the generation has been tested for Semiramis, it still should be tested for others. Besides, we need to test the request of categorical values. It is implemented, but yep we need to test.