that specifies the maximum number of elements in the `structLogs`
output.  This option is useful for debugging a transaction that
involves a large number of repetition.

For example,
```
debug.traceTransaction(tx, {disableStorage: true, limit: 2})
```
shows at most the first two steps in the `structLogs`.

accounts: left pad keybytes-to-encrypt

cmd/utils, node: make datadir reusable for bzzd

README: Changed http:// to https:// on some links

core, trie: replace state caches with trie journal

Changed http:// to https:// on some links in README.md

cmd/utils: don't check for stderr redirect on windows

The redirect check did not work on Go 1.6 and below because Stat
returned an error for stdout and stderr. In Go 1.7 Stat works on stdout
but doesn't return anything meaningful, causing cmd/geth test failures
because the message is printed to stderr only. Fix it by printing to
stdout only.

build: limit test concurrency

TravisCI and AppVeyor run the tests in very slow VMs.
Some of our tests can't cope with that. Running less tests
in parallel should make them somewhat less flakey.

accounts/abi: fix typo in the comment (dummy commit)

State caching

This change introduces a global, per-state cache that keeps account data
in the canon state. Thanks to @karalabe for lots of fixes.

core/state: short-circuit balance change if zero value

light: fix memory expansion bug (same as fix for core/state)

ethclient: bugfix retrieving logs

core/state, light: remove unused StateObject.initCode

core/state: Fix memory expansion bug by not copying clean objects

This change ensures that nodes started with different Name but same
DataDir values don't use the same nodekey and IPC socket.

Port mapper auto discovery used to run immediately after parsing the
--nat flag, giving it a slight performance boost. But this is becoming
inconvenient because we create node.Node for all geth operations
including account management and bare chain interaction. Delay
autodiscovery until the first use instead, which avoids any network
interaction until the node is actually started.

cmd, eth: drop the blockchain version from cli/eth configs

miner: set tx index logs

rpc: format filter ID according to spec for quantities

core/types, ethclient: fix broken subscriptions