Adds change_slots event to notify UI of slot-modifying changes

Created by: stefanoborini

When the model contains options that might modify the resulting slots, a notification must be issued, so that the UI can take appropriate action.

Provides that mechanism, and documents it.

Fixes #74 (closed)

doc/source/plugin_development.rst

@@ -13,14 +13,16 @@ To implement a new plugin, you must
 - define the entity you want to extend (e.g. ``MyOwnDataSource``) as a derived
   class of the appropriate class (e.g. ``BaseDataSource``), and reimplement
   the appropriate methods:
-  - ``run()``: where the actual computation takes place, given the
-    configuration options specified in the model (which is received as an
-    argument). It is strongly advised that the ``run()`` method is stateless.
-  - ``slots()``: must return a 2-tuple of tuples. Each tuple contains instances
-    of the ``Slot`` class. Slots are the input and output entities of the
-    data source or KPI calculator. Given that this information depends on the
-    configuration options, ``slots()`` accepts the model and must return the
-    appropriate values according to the model options.
+
+   - ``run()``: where the actual computation takes place, given the
+     configuration options specified in the model (which is received as an
+     argument). It is strongly advised that the ``run()`` method is stateless.
+   - ``slots()``: must return a 2-tuple of tuples. Each tuple contains instances
+     of the ``Slot`` class. Slots are the input and output entities of the
+     data source or KPI calculator. Given that this information depends on the
+     configuration options, ``slots()`` accepts the model and must return the
+     appropriate values according to the model options.
+
 - Define the model that this ``DataSource`` needs, by extending
   ``BaseDataSourceModel`` and adding, with traits, the appropriate data that
   are required by your data source to perform its task.