feature: Display "Trap" spells on screen to the caster, and optionally display them to all players

[AlexVild]

Is your feature request related to a problem? Please describe.
Trap spells are completely invisible to ALL, at the moment (as of 0.7). This leads to a lot of player confusion when these spells are implemented.

Describe the solution you'd like
The caster should be able to see some map animation based on where they casted the trap, for the duration of the trap, that is looping. Additionally, it would be nice if within the trap spell's options in the Spell Editor, we could toggle "Show Trap to All?", or some equivalent, that would add the map animation for all players, so everyone could see that trap spell.

Getting wild with it, perhaps even:

• Show to all?
• Show to Friendly?

Would be good - or, business logic that says that friendly players can ALWAYS see traps.