replace Web::oEmbed render method with a custom solution

[titanoboa]

replace Web::oEmbed render method with a custom solution:

• for photos, display photo instead of thumnail
• for links, the render method expects 'url' to be part of the response, but according to the foswiki specs the response does not have to include it (you use the url you have requested embedding data for)
• for links, restrict to http(s) links to avoid vulnerability (no javascript:// links etc)