Field order changes when updating schema

## Gentics Mesh Version
- v1.7

## Operating System
- Windows

## JVM
- Oracle JDK 11.0.8

## Problem

I have created a schema with some fields

body type htlm
title type string
metadata type list of strings
twitter card data micro node
url type string
description type string

when I add a new field and change the order of the fields, the order of the fields changes and do no follow the order that I set when I configured the schema

## Expected behaviour and actual behaviour

keep the order of the fields

Start by reproducing the report on Gentics Mesh v1.7: create the schema with the listed fields, add a field, and reorder the existing fields. Compare the configured order with the resulting schema and identify the schema-update entry point; done means the configured field order remains unchanged after the update.

Written by the indexing model from the issue text.