* consensus, miner: stale block supporting

* consensus, miner: refactor seal signature

* cmd, consensus, eth: add miner noverify flag

* cmd, consensus, miner: polish

* miner: commit state which is relative with sealing result

* consensus, core, miner, mobile: introduce sealHash interface

* miner: evict pending task with threshold

* miner: go fmt

* cmd, eth, miner: make recommit configurable

* cmd, eth, les, miner: polish a bit

* miner: filter duplicate sealing work

* cmd: remove uncessary conversion

* miner: avoid microptimization in favor of cleaner code

* miner: regenerate mining work every 3 seconds

* miner: polish

* miner: stream uncle block

* miner: polish

* miner: move agent logic to worker

* miner: polish

* core: persist block before reorg

* consensus/ethash: start remote ggoroutine to handle remote mining

* consensus/ethash: expose remote miner api

* consensus/ethash: expose submitHashrate api

* miner, ethash: push empty block to sealer without waiting execution

* consensus, internal: add getHashrate API for ethash

* consensus: add three method for consensus interface

* miner: expose consensus engine running status to miner

* eth, miner: specify etherbase when miner created

* miner: commit new work when consensus engine is started

* consensus, miner: fix some logics

* all: delete useless interfaces

* consensus: polish a bit

* keystore, ethash, eth, miner, rpc, whisperv6: tech debt with now defunct set.

* whisperv5: swap out gopkg.in/fatih/set.v0 with supported set

params: fix golint warnings

This commit reduces database I/O by not writing every state trie to disk.

* console: fix typo in comment

* contracts/release: fix typo in comment

* core: fix typo in comment

* eth: fix typo in comment

* miner: fix typo in comment

* cmd, consensus, core, miner: instatx clique for --dev

* cmd, consensus, clique: support configurable --dev block times

* cmd, core: allow --dev to use persistent storage too

* core: only fire one chain head per batch

* miner: announce chan events synchronously

* ethdb: add Putter interface and Has method

* ethdb: improve docs and add IdealBatchSize

* ethdb: remove memory batch lock

Batches are not safe for concurrent use.

* core: use ethdb.Putter for Write* functions

This covers the easy cases.

* core/state: simplify StateSync

* trie: optimize local node check

* ethdb: add ValueSize to Batch

* core: optimize HasHeader check

This avoids one random database read get the block number. For many uses
of HasHeader, the expectation is that it's actually there. Using Has
avoids a load + decode of the value.

* core: write fast sync block data in batches

Collect writes into batches up to the ideal size instead of issuing many
small, concurrent writes.

* eth/downloader: commit larger state batches

Collect nodes into a batch up to the ideal size instead of committing
whenever a node is received.

* core: optimize HasBlock check

This avoids a random database read to get the number.

* core: use numberCache in HasHeader

numberCache has higher capacity, increasing the odds of finding the
header without a database lookup.

* core: write imported block data using a batch

Restore batch writes of state and add blocks, tx entries, receipts to
the same batch. The change also simplifies the miner.

This commit also removes posting of logs when a forked block is imported.

* core: fix DB write error handling

* ethdb: use RLock for Has

* core: fix HasBlock comment

* core: remove redundant storage of transactions and receipts

* core, eth, internal: new transaction schema usage polishes

* eth: implement upgrade mechanism for db deduplication

* core, eth: drop old sequential key db upgrader

* eth: close last iterator on successful db upgrage

* core: prefix the lookup entries to make their purpose clearer