Remove href member from Thing Descriptions

[benfrancis]

The Things resource in the Web Thing API includes a href member in each Thing Description which provides a URL to access an individual Thing resource (Thing Description).

In the future we will hopefully change the Things resource to be compliant with the proposed Directory Service API in the WoT Discovery specification, but in the meantime individual Thing resources need not provide the href member since clients which fetch a resource from this URL will already know what the URL is. (It's also currently the same as the id member).

[benfrancis]

I've noticed the href member is also present in Thing resources for some reason.