Start adding editor, fix up sidebar styling

src/app/model/proto-message.model.ts

@@ -0,0 +1,19 @@
+export enum MessageType {
+  String,
+  Boolean,
+  Numeric,
+  List,
+  Map,
+  Object,
+}
+
+export interface ProtoMessageField {
+  name: string;
+  type: MessageType;
+  value: any;
+}
+
+export interface ProtoMessage {
+  name: string;
+  values: ProtoMessageField[];
+}