Why

The Scene Runner did not work correctly, e.g. _gui_input() was never called also key and mouse positions was not correct handled.

What

Revised the handling of input events to ensure that all input events are sent correctly.
Added Input to store the current input event so that it can be accessed via Input.is_... accessible.
Full handled of mouse mask and combination
Added doubleclick handling for mouse button
Drag&Drop test case added
Improved testing of input events
Reset press state to inital state when Scene Runner is released.