When implementing the new bloombits based filter, I've accidentally broke null
topics by removing the special casing of common.Hash{} filter rules, which
acted as the wildcard topic until now.

This PR fixes the regression, but instead of using the magic hash
common.Hash{} as the null wildcard, the PR reworks the code to handle nil
topics during parsing, converting a JSON null into nil []common.Hash topic.

cmd/geth: fix --password typo

core/state: revert log index when removing logs

* p2p: snappy encoding for devp2p (version bump to 5)

* p2p: remove lazy decompression, enforce 16MB limit

This patch fixes the following issues:

* The contract executes send() when it does not have enough balance.
* The contract always sends a total amount of zero.

This commit introduces a network simulation framework which
can be used to run simulated networks of devp2p nodes. The
intention is to use this for testing protocols, performing
benchmarks and visualising emergent network behaviour.

params: enable Byzantium on Ropsten/tests, fix failures

* params: Updated finalized gascosts for ECMUL/MODEXP

* core,tests: Updates pending new tests

* tests: Updated with new tests

* core: revert state transition bugfix

* tests: Add expected failures due to  #15119

consensus, core, params: rebrand Metro to Byzantium

params: add Infura bootnode to Rinkeby

eth/downloader: track peer drops and deassign state sync tasks

cmd/puppeth: reserve "yournode" as a non-allowed ethstats user

light: new CHTs for mainnet and ropsten

eth/downloader: exit loop when there is no more available task

internal/debug: add debug_setGCPercent

* core: only fire one chain head per batch

* miner: announce chan events synchronously