miner: track uncles more aggressively

cmd, core, eth, miner, params: configurable gas floor and ceil

* consensus, miner: stale block supporting

* consensus, miner: refactor seal signature

* cmd, consensus, eth: add miner noverify flag

* cmd, consensus, miner: polish

miner: differentiate between uncle and lost block

* 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: clean up miner startup API, drop noop config field

cmd, core, miner: add --txpool.locals and priority mining

* 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

consensus/clique, light: light client snapshots on Rinkeby