consensus/ethash, cmd/geth: Fix `makedag` epoch

`geth makedag <blocknumber> <path>` was creating DAGs for
`<blocknumber>/<epoch_length> + 1`, hence
it was impossible to create an epoch 0 DAG.

This fixes the calculations in `consensus/ethash/ethash.go` for
`MakeDataset` and `MakeCache`, and applies `gofmt`.

Fixes #14586

The error returned by client.Upload was previously being ignored due to becoming
out of scope outside the if statement. This has been fixed by instead defining a
function which returns the hash and error (rather than trying to set the hash in
each branch of the if statement).

core: Fix VM error logging

Signed-off-by: Lewis Marshall <lewis@lmars.net>

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