Added reference storage system, and command to re-index

Also re-named/orgranized some files for this, to make them "References"
specific instead of a subset of "Util".

database/migrations/2022_08_17_092941_create_references_table.php

@@ -0,0 +1,34 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateReferencesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('references', function (Blueprint $table) {
+            $table->id();
+            $table->unsignedInteger('from_id')->index();
+            $table->string('from_type', 25)->index();
+            $table->unsignedInteger('to_id')->index();
+            $table->string('to_type', 25)->index();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('references');
+    }
+}