Expression reboot

- A3::tokenize recognizes strings, patterns, attr, ops, dates.
- A3::tokenize canonicalizes attributes.

src/commands/Command.cpp

@@ -271,12 +271,6 @@ void Command::filter (std::vector <Task>& input, std::vector <Task>& output)
 /**/
   A3 filt = context.a3.extract_filter ();
   filt.dump ("extract_filter");
-
-  A3 mods = context.a3.extract_modifications ();
-  mods.dump ("extract_modifications");
-
-  A3 words = context.a3.extract_words ();
-  words.dump ("extract_words");
 /**/
 
   Arguments f;