Rename db_ledger to blocktree (#2698)

genesis/src/main.rs

@@ -1,7 +1,7 @@
 //! A command-line executable for generating the chain's genesis block.
 
 use clap::{crate_version, value_t_or_exit, App, Arg};
-use solana::db_ledger::create_new_ledger;
+use solana::blocktree::create_new_ledger;
 use solana::genesis_block::GenesisBlock;
 use solana_sdk::signature::{read_keypair, Keypair, KeypairUtil};
 use std::error;