Rename "state" to "chain_state"

lighthouse/state/chain_config.rs

@@ -1,8 +1,8 @@
-pub struct Config {
+pub struct ChainConfig {
     pub cycle_length: u8,
 }
 
-impl Config {
+impl ChainConfig {
     pub fn standard() -> Self {
         Self {
             cycle_length: 8,

lighthouse/state/mod.rs

@@ -9,7 +9,7 @@ use super::utils;
 pub mod active_state;
 pub mod attestation_record;
 pub mod crystallized_state;
-pub mod config;
+pub mod chain_config;
 pub mod block;
 pub mod crosslink_record;
 pub mod shard_and_committee;