Alternate Poller IP instead of Hostname (#10981)

* optional alternative poller ip

* add missing schema update

* .

* enhance API Call 'add_device' with overwrite_ip key

* .

* .

* updating docs

database/migrations/2019_12_28_180000_add_overwrite_ip_to_devices.php

@@ -0,0 +1,31 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class AddOverwriteIpToDevices extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('devices', function (Blueprint $table) {
+            $table->string('overwrite_ip', 40)->nullable()->after('ip');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('devices', function (Blueprint $table) {
+            $table->dropColumn('overwrite_ip');
+        });
+    }
+}