core/vm: Use a bitmap instead of a map for jumpdest analysis

t push --force

This PR adds a Swarm development environment which can be run in a
Docker container and provides scripts for building binaries and running
Swarm clusters.

accounts/keystore, crypto: don't enforce key checks on existing keyfiles

core: reduce transaction reorganization overhead

ethstats: reduce ethstats traffic by trottling reports

cotnainers/docker: fix the legacy alpine image before dropping

internal/ethapi: add mutex around signing + nonce assignment

This prevents concurrent assignment of identical nonces when automatic
assignment is used.

cmd/puppeth: fix improper key validation for remotes

core: check for gas limit exceeding txs too on new block

consensus/clique: cache block signatures for fast checks

ethstats: don't report transaction content, only hash

cmd, core, eth: configurable txpool parameters

internal/ethapi: fix tx nonces in pool inspect/content

eth: update default gas price when not mining too

eth: don't import propagated blocks during fastsync