WebAgent should allow direct interaction with resource

[bblfish]

The WebAgent may either act directly on the remote resource or via a proxy. For authenticated interaction it may be easier if the user can interact with the remote resource directly.

Otherwise the proxy must be able to authenticate for the user and support all methods.

Direct interaction with the resource on the other hand requires that the remote server authorise access to particular CORS agents.

[bblfish]

It will be easier to start off allowing only edits to the server that published the JS, then to deal with remote resources. This issue is a generalisation to issue #7 "Web Agent should not use Proxy to origin server" in that this is asking for an API that would also allow non proxied access to all resources.