The class property should be added to the textfield

[zhangv]

When we have to put the datetime-picker in the form page, the layout can be quite tricky if we cannot set the class of the inner v-text-field of the datetime-picker. As the display of the component is a v-text-field after all.

[zhangv]

There's a textFieldProps to solve my case. Just wondering if we can make the interface more straightforward.