Add comments, deleted one file that was never used

src/accessors/chain.rs

src/consensus/base.rs

src/consensus/clique/mod.rs

src/consensus/clique/state.rs

src/consensus/mod.rs

src/consensus/pob/demurrage.rs

src/consensus/pob/miner.rs

src/consensus/pob/mod.rs

src/models/chainspec.rs

src/p2p/node/node.rs

src/stagedsync/stage.rs

src/stages/behavior_syncing.rs

src/stages/bodies.rs

src/stages/finish.rs

src/stages/headers.rs

src/stages/interhashes.rs

src/stages/pending_lookup.rs

src/trie/hash_builder.rs