Event-driven dialog queue, story flag command, mod unit tests

Push-based event chains, runtime fixes (single end, goto lifecycle, if,
busy box, held delay, empty options, timed/animated/effect actions), the
'flag name value' DSL command, autoplay --dialogs=N, 19 mod unit tests.

tests/ProbeAction.cs

@@ -0,0 +1,40 @@
+namespace Cthangover.Mods.Dialog.Tests
+{
+    using Cthangover.Mods.Dialog.Action;
+    using Cthangover.Core.UI.Dialog;
+
+    /// <summary>
+    /// Test action that only counts its lifecycle calls: how often the runtime ran,
+    /// constructed and destructed it. Waits for a click by default, so a test can
+    /// park the dialog on it and look at where the runtime stands.
+    /// </summary>
+    public class ProbeAction : ActionCommand
+    {
+        /// <summary>Number of <see cref="DoRun"/> calls.</summary>
+        public int Runs { get; private set; }
+
+        /// <summary>Number of <see cref="DoConstruct"/> calls.</summary>
+        public int Constructs { get; private set; }
+
+        /// <summary>Number of <see cref="DoDestruct"/> calls.</summary>
+        public int Destructs { get; private set; }
+
+        /// <summary>Counts the run.</summary>
+        public override void DoRun(DialogRuntime runtime)
+        {
+            Runs++;
+        }
+
+        /// <summary>Counts the construction.</summary>
+        public override void DoConstruct()
+        {
+            Constructs++;
+        }
+
+        /// <summary>Counts the destruction.</summary>
+        public override void DoDestruct()
+        {
+            Destructs++;
+        }
+    }
+}