User want to have tab index on controls and input fields

[nidin]

What?
User want to have tab index on UIL components to navigate through controls and input field from top to bottom and left to right using tab key.

Why?
At present user need to click on each field using mouse. it is really annoying when editing Vector2, Vector3, Vector4 etc...

How?
Tab index should set automatically set from top to bottom and left to right also API user may override default tab index.