[DatePicker] Support tabbing through a DatePicker field

[bendiy]

Tabbing through a bunch of form fields breaks if there is a DatePicker field. It works fine for a SelectField, but once you tab to a DatePicker field, the tab index reset to the top of the page.

[bendiy]

Perhaps a modal isn't the best approach for every use case:
https://material.angularjs.org/latest/demo/datepicker

[jpetitcolas]

I also prefer the Angular way of handling date picker. Especially if you want to input a date manually.

[oliviertassinari]

Closing for #4787