feat(timetable): handle `absences` property

[Vexcited]

When we're in "Mesure conservatoire", we have those :

{
  "listeAbsences": {
    "_T": 24,
    "V": []
  },
  "listeRetards": {
    "_T": 24,
    "V": []
  },
  "listePunitions": {
    "_T": 24,
    "V": []
  },
  "listeInfirmeries": {
    "_T": 24,
    "V": []
  },
  "joursCycle": {
    "_T": 24,
    "V": [
      {
        "jourCycle": 3,
        "exclusionsEtab": {
          "placeDebut": 60,
          "placeFin": 79,
          "MC": true
        }
      }
    ]
  }
}

When we're absent, it doesn't show in the UI but we can get them in the response :

{
  "listeAbsences": {
    "_T": 24,
    "V": [
      {
        "N": "1#oMFwaR64OBCud0Uho_2_nBFemERhb5tz3rJPrCbPwHA",
        "placeDebut": 60,
        "placeFin": 62,
        "motif": {
          "_T": 24,
          "V": {
            "L": "Motif non encore connu",
            "N": "92#ZMzqOMkFwUc1xfEKaOm4gvmAA4cvRlS7Oia9tH8OYNA",
            "couleur": "#FFFFFF"
          }
        }
      }
    ]
  },
  "listeRetards": {
    "_T": 24,
    "V": []
  },
  "listePunitions": {
    "_T": 24,
    "V": []
  },
  "listeInfirmeries": {
    "_T": 24,
    "V": []
  },
  "joursCycle": {
    "_T": 24,
    "V": [
      {
        "jourCycle": 3
      }
    ]
  }
}