Add Q&A Instructing to use Pandas Dataframes for heterogeneous-type Datasets in Sklearn Khiops Estimators

[popescu-v]

Current Khiops estimators support, via the Dataset object of the Khiops sklearn API, Pandas dataframes and Numpy arrays as data inputs (among other types).

The goal of this issue is to provide motivation / rationale for choosing dataframes over arrays (and other types) and vice-versa. This can take the form of a Q&A stating the trade-offs of each of the dataset table types that are supported by the Khiops sklearn API.