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/ActionTimedUpdateTests.cs

@@ -0,0 +1,40 @@
+namespace Cthangover.Mods.Dialog.Tests
+{
+    using System.Threading.Tasks;
+    using Cthangover.Core.Mods.Testing;
+    using Cthangover.Mods.Dialog.Action.Impls;
+
+    /// <summary>
+    /// <see cref="ActionTimedUpdate"/> completes itself: when its timeline elapses the
+    /// dialog goes on, including the timer of a <c>delay</c> right after it.
+    /// </summary>
+    public class ActionTimedUpdateTests
+    {
+        [ModTest("timed_update/completion_continues_dialog", TimeoutSeconds = 10)]
+        static async Task CompletionContinuesDialog(ModTestContext ctx)
+        {
+            var stage = await DialogStage.Create();
+            try
+            {
+                var timed = new ActionTimedUpdate { WaitTime = 0.1f };
+                var after = new ProbeAction();
+                var dlg = new DialogQueue();
+                dlg.Queue.Add(timed);
+                dlg.Delay(0.1f);
+                dlg.Queue.Add(after);
+
+                stage.Box.SetDialogQueueAndRun(dlg, null, 0, null);
+                ModAssert.True(stage.Box.Runtime.CurrentAction == timed, "dialog waits on the timeline");
+                await DialogStage.Seconds(0.8);
+
+                ModAssert.True(timed.IsDestructed, "timeline is finished and detached");
+                ModAssert.Equal(1, after.Runs, "timeline and the delay after it elapsed, the dialog went on");
+                ModAssert.True(stage.Box.Runtime.CurrentAction == after, "runtime waits on the action after the delay");
+            }
+            finally
+            {
+                stage.Free();
+            }
+        }
+    }
+}