Enable including error messages in API Provider by default

I spent a long time figuring out what's wrong with my integration because I kept only getting error codes. To me it makes more sense to include the error messages by default, because the user might not even know where to enable them. And it's better flow to look for disabling than to not know about a feature that can save time while developing new integrations.
Jira for keeping track of https://github.com/syndesisio/syndesis/issues/8637