Make Decals Linkable with Triggers

[dc-redeclipse]

Sometimes, it's cool to use decals as signs or on display geometry textures when an action occurs, like someone toggling a trigger or approaching one. For example, a door with a button and a display—when the trigger is hit [E], a decal saying "No Entry!" will appear on the screen. For this purpose, a trigger should activate be visible and then end after. A script in the map cfg can introduce a delay, making the decal visible for a defined amount of time by overusing a second trigger.