Fix deprecations

[JelteMX]

Output from deprecations check:

==========================
Calendar widget v4.5  //  Calendar.mpk // calendar/widget/calendar.js
==========================
Possible violations: 5

Violations:
line:213 // column:18 // deprecation:[ mendix.lib.MxObject#getGUID ]
{
    "match": "\t\t\t\t\tobjTitles[obj.getGUID()] = obj.get(this.titleAttr);\r",
    "solution": "mendix/lib/MxObject#getGuid"
}

line:220 // column:18 // deprecation:[ mendix.lib.MxObject#getAttribute ]
{
    "match": "\t\t\t\t\tthisRef = obj.getAttribute(split[0]);\r",
    "solution": "mendix/lib/MxObject#get"
}

line:221 // column:18 // deprecation:[ mendix.lib.MxObject#getGUID ]
{
    "match": "\t\t\t\t\tobjTitles[obj.getGUID()] = thisRef;\r",
    "solution": "mendix/lib/MxObject#getGuid"
}

line:239 // column:27 // deprecation:[ mendix.lib.MxObject#getGUID ]
{
    "match": "\t\t\t\t\t\t\trefTitles[refObjs[i].getGUID()] = refObjs[i].get(split[2]);\r",
    "solution": "mendix/lib/MxObject#getGuid"
}

line:278 // column:23 // deprecation:[ mendix.lib.MxObject#getGUID ]
{
    "match": "\t\t\t\t\t\ttitle: titles[obj.getGUID()],\r",
    "solution": "mendix/lib/MxObject#getGuid"
}

Deprecations need to be fixed before next major MX release