Support import QtQuick.Templates in Components

The QtQuick.Templates module is incredibly useful in Design Studio by enabling me to get the root functionality of Controls like Buttons without the implicit look-and-feel that QtQuick.Controls brings in. But the Templates module does not show up as an option to import.

As a tangent to this, it is unclear what some of the other modules listed are. For example, what is the difference between QtQuick.Controls.impl and the plain QtQuick.Controls module? What about the various styles? Perhaps another task would be to either provide linkage to the Qt documentation on these, or some sort of descriptive text somewhere (tooltip?)