Re-add Observer.register_configuration that was lost due in merge w…

…ith master

kernel_tuner/observers/observer.py

@@ -8,6 +8,11 @@ def register_device(self, dev):
         """Sets self.dev, for inspection by the observer at various points during benchmarking"""
         self.dev = dev
 
+    def register_configuration(self, params):
+        """Called once before benchmarking of a single kernel configuration. The `params` argument is a `dict`
+        that stores the configuration parameters."""
+        pass
+
     def before_start(self):
         """before start is called every iteration before the kernel starts"""
         pass