Introduce 'tell_pending' which replaces 'tell(x, None)'

and I also tackle

• lower_bound <= learner.ask()[0] <= upper_bound
• if we tell(x, y) with x outside the bounds, the point should be added to data, but not any of the other internal datastructures. This will mean that the point will be "invisible" to the learning algorithm, and only useful for plotting and data extraction

for both the Learner1D and Learner2D in that MR. I included this in here to avoid merge conflicts later.

adaptive/learner/integrator_learner.py

@@ -393,6 +393,9 @@ class IntegratorLearner(BaseLearner):
                         assert ival in self.ivals
                         self.priority_split.append(ival)
 
+    def tell_pending(self):
+        pass
+
     def propagate_removed(self, ival):
         def _propagate_removed_down(ival):
             ival.removed = True
@@ -414,8 +417,8 @@ class IntegratorLearner(BaseLearner):
                 self._stack.append(x)
         self.ivals.add(ival)
 
-    def ask(self, n, add_data=True):
-        if not add_data:
+    def ask(self, n, tell_pending=True):
+        if not tell_pending:
             raise NotImplementedError(
                 "Asking points irreversibly changes the learner's data structure.")
         points, loss_improvements = self.pop_from_stack(n)