feat: child xml required for Custom Object

[froucher]

The change set in Custom Object must always contains the following xml properties:

<?xml version="1.0" encoding="UTF-8"?>
<CustomObject xmlns="http://soap.sforce.com/2006/04/metadata">
  ...
  change set
  ...
    <deploymentStatus>Deployed</deploymentStatus>
    <label>CustomObjectTest</label>
    <nameField>
        <label>CustomObjectTest Name</label>
        <type>Text</type>
    </nameField>
    <pluralLabel>CustomObjectTest</pluralLabel>
    <sharingModel>ReadWrite</sharingModel>
</CustomObject>

[amtrack]

closing in favor of #230