Multiple Date selection in calendar

[smitpsanghavi]

I'm submitting a ...

[ ] bug report => Search github for a similar issue or PR before submitting
[x] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Need ability to select multiple dates from p-Calendar.

Current behavior
A single date can be selected using the calendar component.

Expected behavior
Multiple non-consecutive dates can be selected.

What is the motivation / use case for changing the behavior?
We have a case where the user wants to select the dates on which holidays are required to be given. This needs a behaviour where multiple dates need to be taken as input from the calendar.

Please tell us about your environment:
Windows 10, VS 2017, NPM v3.10.9

• Angular version: 4.1.3

• PrimeNG version: 4.0.3

• Browser: all

• Language: TypeScript 2.3.4