Dependencies

- Supports new "depends" attribute.
- Supports "task <id> depends:1,2".
- Supports "task <id> depends:-1,-2".
- Supports id <--> uuid mapping in TDB.

src/Att.cpp

@@ -63,6 +63,7 @@ static const char* modifiableNames[] =
   "recur",
   "until",
   "wait",
+  "depends",
 };
 
 // Synonyms on the same line.