Add support for namespaced attributes in DynamicAttributes

Add support for namespaced attributes in DynamicAttribute with a recursive approach (a DynamicAttribute can have an attribute of type DynamicAttribute). Usage example (both syntaxes are correct):

attrs.get_attr("mem.data.b")
attrs.get_attr("mem").get_attr("data").get_attr("b")

This is a preliminary work in order to introduce a general mechanism for specifiyng backend and export attributes.

• Needs more tests in Python.
• Use snake convention for all attributes naming in C++ and Python.
• Solve #142 (closed)

aidge_core/unit_tests/test_operator_binding.py

@@ -100,6 +100,23 @@ class test_operator_binding(unittest.TestCase):
         attrs.d = 23.89
         self.assertEqual(aidge_core.test_DynamicAttributes_binding_check(attrs), 23.89)
 
+        op = aidge_core.GenericOperatorOp("any_type", 1,0,1)
+        with self.assertRaises(RuntimeError):
+            op.attr.something
+
+        op.attr.something = aidge_core.DynamicAttributes()
+        try:
+            self.assertEqual(str(op.attr), "AttrDict({'something': AttrDict({})})")
+        except Exception:
+            self.fail("op.attr.something raised Exception unexpectedly!")
+
+        op.attr.something.arg1 = 4
+        self.assertEqual(op.attr.something.arg1, 4)
+
+        # auto create the namespace another_thing (not enabled)
+        #op.attr.another_thing.arg = 44
+        #self.assertEqual(op.attr.another_thing.arg, 44)
+
     def test_forward_dims(self):
         in_dims=[25, 25]
         input = aidge_core.Producer(in_dims, name="In")