OverlayGUI (Popups) #38

Description: For the Node Editor to properly work at runtime, we need support for all kinds of popups (GenericMenu, EnumPopup, IntPopup, etc., even Tooltip). This will also fix some bugs regarding node focussing problems, as these will not block user input straight away when clicking it (even the first click event). Additionally, this will open up the possibility to let them account for the zooming - respective built-in controls will simply ignore the GUI scaling:/

State: This is easily possible using the Popup Engine I already made for the GenericMenu to work.

Location: OverlayGUI.cs and RTEditorGUI.cs for implementing new popups