Fleshed out some API endpoints.

- Added the /beacon/validator/block endpoint for GET (untested)
 - Added the /beacon/fork endpoint for GET
 - Cleaned up a bunch of unused imports & variables
 - Removed '/network/block_discovery' endpoint

beacon_node/rest_api/src/helpers.rs

@@ -2,9 +2,7 @@ use crate::{ApiError, ApiResult};
 use beacon_chain::{BeaconChain, BeaconChainTypes};
 use bls::PublicKey;
 use hex;
-use hyper::{Body, Request, StatusCode};
-use serde::de::value::StringDeserializer;
-use serde_json::Deserializer;
+use hyper::{Body, Request};
 use store::{iter::AncestorIter, Store};
 use types::{BeaconState, EthSpec, Hash256, RelativeEpoch, Slot};