core: split out TD from database and all internals

cmd/geth/main.go

core/chain_makers.go

core/chain_manager.go

core/chain_manager_test.go

core/chain_util.go

core/chain_util_test.go

core/genesis.go

core/types/block.go

eth/backend.go

eth/downloader/downloader.go

eth/downloader/downloader_test.go

eth/handler.go

eth/peer.go

eth/protocol.go

miner/worker.go

rpc/api/eth.go

rpc/api/parsing.go

tests/block_test_util.go

xeth/xeth.go