Code Cleanup

- Obsoleted Filter.{h,cpp}.
- Obsoleted Sequence.{h,cpp}.
- Eliminated Context::autoFilter.
- Stubbed Expression::eval.

src/commands/CmdStatistics.cpp

@@ -80,8 +80,7 @@ int CmdStatistics::execute (std::string& output)
   std::vector <Task> tasks;
   context.tdb.lock (context.config.getBoolean ("locking"));
   handleRecurrence ();
-  Filter filter;
-  context.tdb.load (tasks, filter);
+  context.tdb.load (tasks);
   context.tdb.commit ();
   context.tdb.unlock ();