Handle OSM save errors that contain HTML

[EdwardBetts]

Sometimes the OSM API returns errors in plain text, other times in HTML. We assume plain text and escape any HTML.

The system should detect the HTML and handle it in a nicer way.

Example: <h2>This website is under heavy load (queue full)</h2><p>We're sorry, too many people are accessing this website at the same time. We're working on this problem. Please try again later.</p>