Expose scenario states (#168)

* Scenarios (WIP)

* Update ToJson and StatefulBehaviorTests

* fix tests

* Update comment

src/WireMock.Net/Admin/Scenarios/ScenarioStateModel.cs

@@ -0,0 +1,28 @@
+namespace WireMock.Admin.Scenarios
+{
+    /// <summary>
+    /// ScenarioStateModel
+    /// </summary>
+    public class ScenarioStateModel
+    {
+        /// <summary>
+        /// Gets or sets the name.
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// Gets or sets the NextState.
+        /// </summary>
+        public string NextState { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this <see cref="ScenarioStateModel"/> is started.
+        /// </summary>
+        public bool Started { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this <see cref="ScenarioStateModel"/> is finished.
+        /// </summary>
+        public bool Finished { get; set; }
+    }
+}