Chat upgraded for dice rolls and system messages

src/app/chat/entry/entry.ts

@@ -0,0 +1,25 @@
+export abstract class Entry {
+  public timestamp;
+
+  protected constructor() {
+    this.timestamp = new Date();
+  }
+}
+
+export class SystemMessage extends Entry {
+
+  constructor(public message: string,
+              public severity: SeverityEnum) {
+    super();
+  }
+
+  public get type(): string {
+    return 'system'
+  }
+}
+
+export enum SeverityEnum {
+  info = 'info',
+  warning = 'warning',
+  error = 'error',
+}