feat(calendar): add eventDates support and onSelect handler

[lubber-de]

Description

This PR adds support for eventDates and a new event handler onSelect to provide individual functionality whenever a cell-item was clicked.
This works similar as disabledDates by providing the option to set a tooltip given a message to a date cell.In addition a given class can be added to the cell. Otherwise a default eventClass (default blue) will be added to every event-cell.

Example using individual className for eventDate cells

$('.ui.calendar').calendar({
eventDates: [
    {
      date: new Date(2019,3,21),
      message: 'Show me in light purple',
      class: 'inverted purple'
    },{
      date: new Date(2019,3,22),
      message: 'Show me in green',
      class: 'green'
    }
]
});

Example using default className for each event

$('.ui.calendar').calendar({
eventClass: 'inverted red',
eventDates: [
    new Date(2019,3,20), //no message tooltip
    {
      date: new Date(2019,3,21),
      message: 'I got the default color (light red)'
    },{
      date: new Date(2019,3,22),
      message: 'Me too'
    }
]
});

Example using onSelect event handler

$('.ui.calendar').calendar({
onSelect: function(date,mode) {
  console.log('You have chosen',date,'in mode',mode);
  if(mode!=='day') {
    console.log('You cannot select anything else than a day!');
    return false;
  }
}
});

Testcase

eventDates

http://jsfiddle.net/nc0yutq2/

onSelect

http://jsfiddle.net/c7kLvef4/

Screenshot

Closes

#674

[lubber-de]

Btw: This PR also fixes the issue from #574 (check for undefined after parsing date) without the extra logging. I did this because the other PR did not receive any more feedback from the author since 2 weeks and the fix was only one LOC.

[lubber-de]

Last commit adds event handler onSelect

[prudho]

LGTM

[y0hami]

LGTM

[exoego]

LGTM

[ColinFrick]

LGTM