Add required property to AutoComplete, Spinner and InputMask

[dhniels]

I'm submitting a ... (check one with "x")

[x] feature request 

What is the motivation / use case for changing the behavior?
Looking at the documentation on PrimeNG site, it appears that p-dropdown has a "required" property, but the autocomplete does not. It seems highly important that required also be a property of autocomplete because it something that would be used in forms. In my case, I have in several places autocompletes inside table cells that I would like to set to required and use angulars built in validation classes to style them.

• Angular version: 4.3.1

• PrimeNG version: 4.1.1

[progmancod]

Please, this is very important!

[dhniels]

Is there any workaround way to do this until the feature is added? Its very important in our application as we have several autocompletes that need a required attribute.

[jonatino]

I would like this as well!