create a prometheus exporter on a standard http port (#107)

* create a hyper server and add option to enable it in config

* move prometheus stuff to its own file; update format

* create metric type and help lookup table

* finish the metric help type map

* switch to a boolean and a standard port

* dont emit unimplemented metrics

* fail if curl returns a non 200

* resolve conflicts

* move log out of config.show and into main

* terminating new line

* upgrade curl

* include unimplemented stats

Cargo.toml

@@ -31,3 +31,5 @@ base64 = "0.13"
 stringprep = "0.1"
 tokio-rustls = "0.23"
 rustls-pemfile = "1"
+hyper = { version = "0.14", features = ["full"] }
+phf = { version = "0.10", features = ["macros"] }