Make optional application-related registration parameters optional

This commit makes optional registration parameters optional; They should only be filled in after the user has submitted an application. The application will crash during registration without these parameters being optional, and adding them to the form would be illogical.

database/migrations/2014_10_12_000000_create_users_table.php

@@ -19,8 +19,8 @@ class CreateUsersTable extends Migration
             $table->string('name');
             $table->string('email')->unique();
             $table->timestamp('email_verified_at')->nullable();
-            $table->string('username'); // Mojang Username
-            $table->date('dob');
+            $table->string('username')->nullable(); // Mojang Username
+            $table->date('dob')->nullable();
             $table->ipAddress('originalIP');
             $table->string('password');
             $table->rememberToken();