Adding the gini impurity to nodes in Model

- Adding the gini impurity to each node in Tree
- Adding methods to filter leaves above an impurity threshold
- Adding the LISP filter associated to the patch in each leaf
- Fixing the attributes in Model, Cluster and Anomaly to be reachable
  with dir
- Fixing the resource_id attribute in Model, Cluster and Anomaly when
  they are built from a JSON structure
passing the filter to tree's get_leaves would be a bit more efficient