* accounts/keystore: add timeout to test to prevent failure on travis

The TestWalletNotifications test sporadically fails on travis.
This is because we shutdown the event collection before all events are received.
Adding a small timeout (10 milliseconds) allows the collector to be scheduled
and to consume all pending events before we shut it down.

* accounts/keystore: added newlines back in

* accounts/keystore: properly fix the walletNotifications test

* accounts/keystore: fix race in Import/ImportECDSA

* accounts/keystore: added import/export tests

* cmd/geth: improved TestAccountImport test

* accounts/keystore: added import/export tests

* accounts/keystore: fixed naming

* accounts/keystore: fixed typo

* accounts/keystore: use mutex instead of rwmutex

* accounts: use errors instead of fmt

The accountCache contains a file cache, and remembers from
scan to scan what files were present earlier. Thus, whenever
there's a change, the scan phase only bothers processing new
and removed files.

- Handle a data race where a Ledger drops between list and open
- Prolong Ledger tx confirmation window to 30 days from 1 minute
- Simplify Ledger chainid-signature calculation and validation
- Simplify Ledger USB APDU request chunking algorithm
- Silence keystore account cache notifications for manual actions
- Only enable self derivations if wallet open succeeds

go get github.com/gordonklaus/ineffassign
ineffassign .

- Sign takes common.Address, not Account
- Import/Export methods work with encrypted JSON keys

In order to avoid disk thrashing for Accounts and HasAccount,
address->key file mappings are now cached in memory. This makes it no
longer necessary to keep the key address in the file name. The address
of each key is derived from file content instead.

There are minor user-visible changes:

- "geth account list" now reports key file paths alongside the address.
- If multiple keys are present for an address, unlocking by address is
  not possible. Users are directed to remove the duplicate files
  instead. Unlocking by index is still possible.
- Key files are overwritten written in place when updating the password.

- Manager.Accounts no longer returns an error.
- Manager methods take Account instead of common.Address.
- All uses of Account with unkeyed fields are converted.

The account management API was originally implemented as a thin layer
around crypto.KeyStore, on the grounds that several kinds of key stores
would be implemented later on. It turns out that this won't happen so
KeyStore is a superflous abstraction.

In this commit crypto.KeyStore and everything related to it moves to
package accounts and is unexported.

This should fix the flakeyness.

I forgot to update one instance of "go-ethereum" in commit 3f047be5.

All code outside of cmd/ is licensed as LGPL. The headers
now reflect this by calling the whole work "the go-ethereum library".

While here, also improve the docs and speed up the tests.
The tests used the scrypt keystore with ridiculous settins and took 20s
each.

* chronological order of creation
* new naming scheme keystore/UTC--<created_at UTC ISO8601>-<address hex>
* KeyStore2 -> KeyStore
* backward compatibility
* refactor keyStore methods

* multiple passwords allowed in password file
* split on "\n", sideeffect: chop trailing slashes. fixes common mistake <(echo 'pass')
* remove accounts.Primary method
* do not fall back to primary account for mining

There is no point to using time.Duration if the value is interpreted as
milliseconds. Callers should use the standard multiplication idiom to
choose the unit. In fact, the only caller outside of the tests already
does so.

Account is now always a non-pointer. This will be important once
the manager starts remembering accounts.

AccountManager is now always a pointer because it contains locks
and locks cannot be copied.

* Use RWMutex instead of Mutex
* Use time.Duration instead of int for unlock time
* Use time.After with select instead of time.Sleep

* Change account signing API to two sign functions;
  Sign without passphrase - works if account is unlocked
  Sign with passphrase - always works and unlocks the account
* Account stays unlocked for X ms and is then automatically locked

Thanks to https://github.com/jaekwon for original fix!

* Use crypto.Sign instead of directly calling secp256k1 lib
* Rename UserAccount to Account and Addr to Address (for consistency)
* Change AccountManager.Sign to take ptr to Account instead of
  address byte array
* Simplify copying of Accounts in Accounts()
* PubkeyToAddress and GetEntropyCSPRNG now exported

* Add initial UserAccount and AccountManager structs
* Add NewAccount, Sign and Accounts functions
* Refactor key stores to use key address as main identifier
  while keeping the UUID.
* Use key address as file/dir names instead of UUID