Enhancement - Command Line Parsing

- Fixed problem where a blank ID was considered valid.  For example,
  the command "task 1 -2" should use -2 as the description, but instead
  considered this to be the sequence 1,0,2.
- Replaced old validId calls with the new validSequence calls.
- A sequence has been redefined to be the first set of consecutive
  arguments that look like sequences.  Once broken by a non-sequence
  argument, all remaining args, even if they look like a sequence,
  are not considered part of the sequence.  This allows commands like
  "task append 1,3-5 Write 10 emails", where 10 is not part of the
  sequence because of the intervening "Write".
- Unit tests (parse.t.cpp) that exercise the parsing of sequences.
  Should probably be expanded to cover more.

src/tests/.gitignore

@@ -5,3 +5,4 @@ date.t
 duration.t
 text.t
 autocomplete.t
+parse.t