Adapted ROC CMS to concurrent EWF.

Revisited the shared logger to reduced number of useless calls.

src/persistence/cms_storage.e

@@ -39,6 +39,13 @@ feature -- Status report
 		deferred
 		end
 
+feature -- Basic operation
+
+	close
+			-- Close/disconnect current storage.
+		deferred
+		end
+
 feature -- Error Handling
 
 	error_handler: ERROR_HANDLER

src/persistence/cms_storage_null.e

@@ -45,6 +45,13 @@ feature -- Status report
 			Result := True
 		end
 
+feature -- Basic operation
+
+	close
+			-- <Precursor>
+		do
+		end
+
 feature -- URL aliases
 
 	set_path_alias (a_source: READABLE_STRING_8; a_alias: READABLE_STRING_8)