Holiday calendar added

[Shruti-Apte]

closes #1796

[apoorv1316]

The holiday calendar is showing the date on which user applied for the holiday and not the actual holiday date. So, if republic holiday is on 26 January but the user added the holiday entry for it on 10th April then the calendar will show the 10th April as holiday and if the user has not applied for that holiday then that holiday won't shown in the calendar.
@Shruti-Apte @sonamvg @prasanthchaduvula

[Shruti-Apte]

@apoorv1316
According to me, To make sure users always select the correct holiday date, we can auto-populate the date field based on the selected holiday. i.e 26 jan for republic day should be auto-populated and must be a non-editable field on time off entries

cc: @sonamvg @prasanthchaduvula

[sonamvg]

The calendar should show a list as per holidays updated by the Org admin as reflected in settings page.
This is to address the concern of showing list of holidays and optional holidays to employee.