Support times for due dates

[untitaker]

• Todoman should introduce a time_format configuration parameter that, if non-empty, is additionally used to format due datetimes. It should be omitted if DUE does not have a time component.
• Todoman should prevent people from using %H, %Mand so on indate_format` (I'm currently doing that)
• Likewise it should prevent people from using %Y etc in time_format

[WhyNotHugo]

Okay, so this makes sense. I was actually thinking of additional changes that contribute to this:

1. Make compact_format configurable (via the configuration file -- no cli flag).
2. Introduce a new time_format setting (as you suggested).
3. Change compact_format to include separate due_date and due_time component: {id:3d} [{completed}] {urgent} {due_date} {due_time} {summary} {list}{percent}. I'm not sure if I want to change the default or not. What I am sure of, is that it'll allow you to retain you current output. 😉
4. The "today"/"tomorrow" thingy will only replace due_date, having no effect on the time (we'll probably add Formatter.parse_time.
5. Double check how all this affects --porcelain (tests will quickly squeal if we break it though).

[untitaker]

I'm labelling this hard because of the introduction of compact_format. I don't think --porcelain will be affected by this at all. It ignores all format options.

[WhyNotHugo]

I just realized we need to implement this for #108 to work/make sense (for some reason I'd assumed we'd done this already).

[untitaker]

I don't understand what you mean. What did you think was implemented already?

[WhyNotHugo]

Well, without date/time separation (the suggestion here), the code for #108 won't work, because format_date actually receives a datetime object.

[untitaker]

#117 fixes this. I chose a route that doesn't implement a config option for compact_format. The dt_separator is necessary in either case because we need to use it for parsing input as well.