Makes Interface interface a bit more stateless and abstract.

Obviously this change is dictated by EVMC design. The EVMC tries to keep the responsibility for EVM features totally inside the VMs, if feasible. This makes VM "stateless" because VM does not need to pass any information between executions, all information is included in parameters of the execute function.

* consensus, miner: stale block supporting

* consensus, miner: refactor seal signature

* cmd, consensus, eth: add miner noverify flag

* cmd, consensus, miner: polish

* 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

This PR enables the indexers to work in light client mode by
downloading a part of these tries (the Merkle proofs of the last
values of the last known section) in order to be able to add new
values and recalculate subsequent hashes. It also adds CHT data to
NodeInfo.

* 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

* all: simplify switches

* silly mistake

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

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

The current trie memory database/cache that we do pruning on stores
trie nodes as binary rlp encoded blobs, and also stores the node
relationships/references for GC purposes. However, most of the trie
nodes (everything apart from a value node) is in essence just a
collection of references.

This PR switches out the RLP encoded trie blobs with the
collapsed-but-not-serialized trie nodes. This permits most of the
references to be recovered from within the node data structure,
avoiding the need to track them a second time (expensive memory wise).

* eth: made changes to conform better to the golint standards

* eth: fix comment nit

* core: improve getBadBlocks to return full block rlp

* core, eth, ethapi: changes to getBadBlocks formatting

* ethapi: address review concerns

* tracing: fix minor off-by-one error

* tracers: go generate

* core, eth, trie: streaming GC for the trie cache

* trie: track memcache statistics

This removes a golint warning: type name will be used as trie.TrieSync by
other packages, and that stutters; consider calling this Sync.

In hexToKeybytes len(hex) is even and (even+1)/2 == even/2, remove the +1.

This commit adds many comments and removes unused code.
It also removes the EmptyHash function, which had some uses
but was silly.

* all: get rid of error when create mdb

* core: clean up variables definition

* all: inline mdb definition