Add list detectors endpoint

[gkumbhat]

Description

As we are starting to support more and more detectors, it would be useful for user to be able to list all the available detectors by just making an API call.

The information we should return for this:

1. Detector id
2. Detector type
3. Associated chunker type / id

With a request parameter, we should also enable following in same endpoint:

1. hostname + port