Penalty time in RELTIME

Contest penalty_time is the only time that's in integer minutes, and one of only 3 places where we even say minutes in the spec. As per issue icpc#150, it also blocks non-integer penalty times.

This changes it to use RELTIME, which improves both issues. It does not attempt to address anything else in issue 150, namely no attempt to add additional scoring algorithms.

Contest_API.md

@@ -754,7 +754,7 @@ Properties of contest objects:
 | scoreboard\_freeze\_duration | RELTIME ?       | How long the scoreboard is frozen before the end of the contest. Defaults to `0:00:00`.
 | scoreboard\_thaw\_time       | TIME ?          | The scheduled thaw time of the contest, may be `null` if the thaw time is unknown or not set.
 | scoreboard\_type             | string          | What type of scoreboard is used for the contest. Must be either `pass-fail` or `score`.
-| penalty\_time                | integer         | Penalty time for a wrong submission, in minutes. Only relevant if scoreboard\_type is `pass-fail`.
+| penalty\_time                | RELTIME         | Penalty time for a wrong submission. Only relevant if scoreboard\_type is `pass-fail`.
 | banner                       | array of FILE ? | Banner for this contest, intended to be an image with a large aspect ratio around 8:1. Only allowed mime types are image/\*.
 | logo                         | array of FILE ? | Logo for this contest, intended to be an image with aspect ratio near 1:1. Only allowed mime types are image/\*.
 | location                     | LOCATION ?      | Location where the contest is held.
@@ -815,7 +815,7 @@ Returned data:
    "duration": "5:00:00",
    "scoreboard_freeze_duration": "1:00:00",
    "scoreboard_type": "pass-fail",
-   "penalty_time": 20,
+   "penalty_time": "0:20:00",
    "banner": [{
        "href": "https://example.com/api/contests/wf2014/banner",
        "filename": "banner.png",
@@ -840,7 +840,7 @@ Returned data:
    "countdown_pause_time": "0:03:38.749",
    "duration": "2:30:00",
    "scoreboard_type": "pass-fail",
-   "penalty_time": 20
+   "penalty_time": "0:20:00"
 }
 ```