This PR adds enode.LocalNode and integrates it into the p2p
subsystem. This new object is the keeper of the local node
record. For now, a new version of the record is produced every
time the client restarts. We'll make it smarter to avoid that in
the future.

There are a couple of other changes in this commit: discovery now
waits for all of its goroutines at shutdown and the p2p server
now closes the node database after discovery has shut down. This
fixes a leveldb crash in tests. p2p server startup is faster
because it doesn't need to wait for the external IP query
anymore.

This fixes a rare deadlock with the inproc adapter:

- A node is stopped, which acquires Network.lock.
- The protocol code being simulated (swarm/network in my case)
  waits for its goroutines to shut down.
- One of those goroutines calls into the simulation to add a peer,
  which waits for Network.lock.

The fix for the deadlock is really simple, just release the lock
before stopping the simulation node.

Other changes in this PR clean up the exec adapter so it reports
node startup errors better and remove the docker adapter because
it just adds overhead.

In the exec adapter, node information is now posted to a one-shot
server. This avoids log parsing and allows reporting startup
errors to the simulation host.

A small change in package node was needed because simulation
nodes use port zero. Node.{HTTP,WS}Endpoint now return the live
endpoints after startup by checking the TCP listener.

internal/ethapi: warn on failed account accesses

Notifier tracks whether subscription are 'active'. A subscription
becomes active when the subscription ID has been sent to the client. If
the client sends notifications in the request handler before the
subscription becomes active they are dropped. The tests tried to work
around this problem by always waiting 5s before sending the first
notification.

Fix it by buffering notifications until the subscription becomes active.
This speeds up all subscription tests.

Also fix TestSubscriptionMultipleNamespaces to wait for three messages
per subscription instead of six. The test now finishes just after all
notifications have been received and doesn't hit the 30s timeout anymore.

These minor changes already shaved off around 30s.

* swarm/storage: lower constants for faster tests

* swarm: reduce test size for TestLocalStoreAndRetrieve

* swarm: reduce nodes for dec_inc_node_count

* cmd/clef: encrypt master seed of clef

Signed-off-by: YaoZengzeng <yaozengzeng@zju.edu.cn>

* keystore: refactor for external use of encryption

* clef: utilize keystore encryption, check flags correctly

* clef: validate master password

* clef: add json wrapping around encrypted master seed

* swarm/network/stream: introduced visualized snapshot sync test

* swarm/network/stream: non-existing hash visualization sim

* swarm/network/stream: fixed retrieval tests; new backend for visualization

* swarm/network/stream: cleanup of visualized_snapshot_sync_sim_test.go

* swarm/network/stream: rebased PR on master

* swarm/network/stream: fixed loop logic in retrieval tests

* swarm/network/stream: fixed iterations for snapshot tests

* swarm/network/stream: address PR comments

* swarm/network/stream: addressed PR comments

* travis: exclude non-test jobs for PRs

We don't usually look at these builders and not starting them
removes ~15min of build time.

* build: don't run vet before tests

Recent versions of Go run vet during 'go test' and we have
a dedicated lint job.

* build: use -timeout 5m for tests

Tests sometimes hang on Travis. CI runs are aborted after 10min with no
output. Adding the timeout means we get to see the stack trace for
timeouts.

This fixes the tests on 32bit platforms.

This is a stopgap until new tests have been generated and imported.

* core/vm : fix failing testcase

* core/vm: fix nitpick

eth/downloader: fix invalid hash chain error due to head mini reorg

* core/vm: create2 address generation tests

* core/vm: per byte cost of CREATE2

* core/vm: fix linter issue in test

params: add ropsten fork delay, update les checkpoints

* core/vm/runtim: benchmark create/create2

* core/vm: do less hashing in CREATE2

* core/vm: avoid storing jumpdest analysis for initcode

* core/vm: avoid unneccesary lookups, remove unused fields

* core/vm: go formatting tests

* core/vm: save jumpdest analysis locally

* core/vm: use common.Hash instead of nil, fix review comments

* core/vm: removed type destinations

* core/vm: correct check for empty hash

* eth: more elegant api_tracer

* core/vm: address review concerns

Enable constantinople on Ropsten testnet

* cmd/puppeth: fix node URL in health check

* cmd/puppeth: set external IP for geth

* cmd/puppeth: fix enode cast issue

swarm/storage/feeds: Renamed MRU to Swarm Feeds