Explosions and Grenades, Triggers, OnDestroy, OnExAct, Fueltanks and destructible tables (#247)

* initial explosiveComponent

* remove garbagee

* assets

* tile mass deletion baby

* grenades

* tweaks

* Update Content.Server/GameObjects/Components/Explosion/ExplosiveComponent.cs

Co-Authored-By: Pieter-Jan Briers <pieterjan.briers@gmail.com>

* Ex_act based on damage, fixes and tweaks

* One finishing touch

Done the most cringe way

* ex_act explosions, tables are destructible now

also adds fuel tanks

* adds ex_act to mobs

Content.Server/GameObjects/EntitySystems/TriggerSystem.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Linq;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects.Systems;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Timers;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    /// <summary>
+    /// This interface gives components behavior when being "triggered" by timer or other conditions
+    /// </summary>
+    public interface ITimerTrigger
+    {
+        /// <summary>
+        /// Called when one object is triggering some event
+        /// </summary>
+        bool Trigger(TimerTriggerEventArgs eventArgs);
+    }
+
+    public class TimerTriggerEventArgs : EventArgs
+    {
+        public IEntity User { get; set; }
+        public IEntity Source { get; set; }
+    }
+
+    [UsedImplicitly]
+    public sealed class TriggerSystem : EntitySystem
+    {
+        public void HandleTimerTrigger(TimeSpan delay, IEntity user, IEntity trigger)
+        {
+
+            Timer.Spawn(delay, () =>
+            {
+                var timerTriggerEventArgs = new TimerTriggerEventArgs
+                {
+                    User = user,
+                    Source = trigger
+                };
+                var timerTriggers = trigger.GetAllComponents<ITimerTrigger>().ToList();
+
+                foreach (var timerTrigger in timerTriggers)
+                {
+                    if (timerTrigger.Trigger(timerTriggerEventArgs))
+                    {
+                        // If an IOnTimerTrigger returns a status completion we finish our trigger
+                        return;
+                    }
+                }
+            });
+        }
+    }
+}