* Add multi-dataset support, replacing **SET_USER_DB** by **setBackground()**, **setForeground()**
* Added **freezeParams()** to freeze parametric dataset for specific scenario to be used by non parametric tools or other foreground datasets.
* Added dataset parameters : parameters scoped to a specific dataset, with scope / conflict resolution of parameters with same names.
* Added extended import / export of datasets with their parameters : **export_db()**, **import_db()**
* Added non regression tests