Added common.GetAlternatePlayTime for Sebastian

below is sample calls for a game with 2 45 minute periods and 2 15
minute OTs...
1, "42:08" -> 42:08
1, "47:08" -> 45:00 (+2)
2, "74:23" -> 74:23
2, "91:23" -> 90:00 (+1)
3, "108:23" -> 105:00 (+3)
4, "124:23" -> 120:00 (+4)