[Feature] Create module that loads example datasets

[mdenker]

Feature
Based on the datasets module, which handles downloading the datasets from datasets.python-elephant.org, one could image to have a function that is more intuitive for a user to download example datasets to play around with. For example, one could image something like:

elephant.datasets.download_tutorial_data(13)

or

elephant.datasets.download_tutorial_data("some_telling_name_for_the_dataset")