The Overlay-Element define overlay components. 
It is possible to set severals image and text overlays at a specific position on screen.
The position can be relative to the the screen size.
The image switch if clicked by mouse. The text will be writable if clicked my mouse.
If Overlay-element is sent a %text-message% if the text was clicked.
The a text can change by command a %text-message%.
The screen can have a background color (transparency do not work yet!).
It must be a child of a %render-element%.