- add message class for help texts

- add migrations for message class
- load messages into vue form for dataset publishing
- check unique email of authors during dataset creation
- adaptions in create-step1.blade.php for tooltip colors
- updated package.json

database/migrations/2020_01_27_125513_create_messages_table.php

@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class CreateMessagesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('messages', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('metadata_element', 255);
+            $table->text('help_text');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('messages');
+    }
+}