Moved bundle_id to ids and aggregated ExtensionPointID onto enumeration class

Created by: stefanoborini

Extracted the bundle_id and the extension point ids due to their shared nature.

Fixes #24 (closed)

doc/source/api/force_bdss.data_sources.rst

 force_bdss.data_sources package
 ===============================
 
+Subpackages
+-----------
+
+.. toctree::
+
+    force_bdss.data_sources.tests
+
 Submodules
 ----------
 
@@ -12,6 +19,14 @@ force_bdss.data_sources.base_data_source module
     :undoc-members:
     :show-inheritance:
 
+force_bdss.data_sources.base_data_source_bundle module
+------------------------------------------------------
+
+.. automodule:: force_bdss.data_sources.base_data_source_bundle
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
 force_bdss.data_sources.base_data_source_model module
 -----------------------------------------------------