feat: add saveable thing for saving user/client data

Closes #12

src/core/base/SaveableThing.ts

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2018, 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import {SCThing, SCThingUserOrigin} from '../Thing';
+
+/**
+ * An encapsulation of the data (e.g. a thing) that is saved, which provides additional information.
+ */
+export interface SCSaveableThing<T extends SCThing> extends SCThing {
+  /**
+   * The contained data
+   */
+  data: T;
+
+  /**
+   * Type of the origin
+   */
+  origin: SCThingUserOrigin;
+}