* signer: properly handle terminal escape characters

* log: use strconv conversion instead of custom escape function

* log: remove relection tests for nil

* log: delete RotatingFileHandler

We added this for the dashboard, which is gone now. The
handler never really worked well and had data race and file
handling issues.

* internal/debug: remove unused RotatingFileHandler setup code

docs: change http to https on links in log/README.md

* log: Do not pad too long values

* log: gofmt

- update go-colorable, go-isatty, go-runewidth packages
- use go-isatty instead of log/term and remove log/term package

* cmd, dashboard, internal, log, node: logging feature

* cmd, dashboard, internal, log: requested changes

* dashboard, vendor: gofmt, govendor, use vendored file watcher

* dashboard, log: gofmt -s -w, goimports

* dashboard, log: gosimple

- Keep the tailing zeros.
- Limit precision to milliseconds.

This commit adds all changes needed for the merge of swarm-network-rewrite.
The changes:

- build: increase linter timeout
- contracts/ens: export ensNode
- log: add Output method and enable fractional seconds in format
- metrics: relax test timeout
- p2p: reduced some log levels, updates to simulation packages
- rpc: increased maxClientSubscriptionBuffer to 20000

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

This ensures 'make test' finds all errors that remote CI would find.
Go 1.7 vet reports a false positive in package log, add a workaround.

Also tweak behaviour so colors are only enabled when stderr is a terminal.