Provide a Detector JAXRS endpoint

As identified in TIKA-1335, the Tika Server now has an endpoint which will tell you what Detectors are available to it, but not one that will trigger detection. That means your only way to do detection is to request the metadata, and check the content type, but that isn't always as accurate as an explicit detection call (eg if a general parser picks up the file)

We should therefore add in a new endpoint that just does the detection