Scripting - Enabled scripting (#638)

* Scripting - Simplified view model structure
* Scripting - Removed Layer and LayerProperty scripts

src/Artemis.UI.Shared/Plugins/ScriptingProviders/ScriptEditorViewModel.cs

@@ -8,13 +8,49 @@ namespace Artemis.UI.Shared.ScriptingProviders
     /// </summary>
     public class ScriptEditorViewModel : Screen, IScriptEditorViewModel
     {
-        /// <inheritdoc />
-        public ScriptEditorViewModel(Script script)
+        private Script? _script;
+
+        /// <summary>
+        ///     Creates a new instance of <see cref="ScriptEditorViewModel" />
+        /// </summary>
+        /// <param name="scriptType">The script type this view model was created for</param>
+        public ScriptEditorViewModel(ScriptType scriptType)
+        {
+            ScriptType = scriptType;
+        }
+
+        /// <summary>
+        ///     Called just before the script is changed to a different one
+        /// </summary>
+        /// <param name="script">The script to display or <see langword="null" /> if no script is to be displayed</param>
+        protected virtual void OnScriptChanging(Script? script)
+        {
+        }
+
+        /// <summary>
+        ///     Called after the script was changed to a different one
+        /// </summary>
+        /// <param name="script">The script to display or <see langword="null" /> if no script is to be displayed</param>
+        protected virtual void OnScriptChanged(Script? script)
         {
-            Script = script;
         }
 
         /// <inheritdoc />
-        public Script Script { get; }
+        public ScriptType ScriptType { get; }
+
+        /// <inheritdoc />
+        public Script? Script
+        {
+            get => _script;
+            internal set => SetAndNotify(ref _script, value);
+        }
+
+        /// <inheritdoc />
+        public void ChangeScript(Script? script)
+        {
+            OnScriptChanging(script);
+            Script = script;
+            OnScriptChanged(script);
+        }
     }
 }