child elements on the DynamicHTTPMetadataProvider type

[Rod Widdowson]

> Btw, I replaced <security:TrustEngine> with <TLSTrustEngine> on the
> MetadataConfiguration page [1] since this aligns with the rest of the
> docs as well as the schema. Can you check this too?

No.  That <TrustEngine> is deprecated and is about the Signature Filter.  It's a legacy from V2 RelyParty Syntax.  The
<TLSTrustEngine> is only relevant to the two HTTP providers.

I'll remove that from the documentation, add it to the deprecation pages and change the code appropriately.

> Thanks Rod. When you get a chance, will you check my work?

I'd actually prefer not to right now or I'll get code blind.  The easiest way to get  this reviewed would be to let the list know
when you are done and what pages changed, then I/we can go over the documentation against the code.  

Thanks