Add clickThrough property to GuiWindow

[thecreare]

Allows windows to not sink clicks, fixes #2162
Should this also apply to the chat window?

[Argmaster]

So, I don't know if this was blessed by @IntegratedQuantum or not but I would like to point out that this is a workaround which special cases very specific behavior. Instead I think it should be implemented through storing windows and components in a tree hierarchy and doing an event (as in event propagation (as in propagation ) through them to have a robust solution that won't require changes the second we want movement to be possible when UI is open or to stop character from shifting when text input is active.

[IntegratedQuantum]

Disabling all inputs is not going to work since that makes it impossible to scale/move the crosshair (and all other windows, please think of the debug windows too).

As @Argmaster pointed out we need better event handling, events are already propagated through the tree, we just need a way to know whether the event was handled or not (see also #2144), if it wasn't handled then it should go on.

To fix the crosshair you then also just need to consult the hasBackground property.

[IntegratedQuantum]

I have made a more robust implementation, based on what @Argmaster suggested, in #2511