Prometheus HTTP SD Server

[hartfordfive]

Hi everyone,

With the addition of the http service discovery being added in v2.28, I've decided to create a new HTTP SD server to address a requirement I had to allow for a more simplistic approach of adding/removing targets and labels when other conventional service discovery methods aren't possible or desired.   The current v.0.1.0 release only supports local storage, thus isn't highly available although I'm in the process of adding the ability to use an external Consul KV datastore.  I realize there are still quite a few improvements that need to be made (create appropriate tests, add more external data stores, code optimizations, etc) although I figured I'd mention it in this group in case there's any interest.  

Constructive feedback, suggestions and feature requests are welcomed!

Al