There are several places where we're using a *search.Handler, when we
only want to be able to do query and describe requests. When these
places need to be moved also out of the context of camlistored, (like
when making a server app such as the publisher), the QueryDescriber can
be used, and the adequate implementation (*search.Handler,
*client.Client, or any other) is used depending on the context.
Change-Id: Ie1c5bb6f1bbba32c24a8eb2d1175af95ffcc8335
mpl