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.

These changes make prompting behave consistently on all platforms:

* The input buffer is now global.
  Buffering was previously set up for each prompt, which can cause weird
  behaviour, e.g. when running "geth account update <input.txt" where
  input.txt contains three lines. In this case, the first password
  prompt would fill up the buffer with all lines and then use only the
  first one.

* Print the "unsupported terminal" warning only once.
  Now that stdin prompting has global state, we can use it to track
  the warning there.

* Work around small liner issues, particularly on Windows.
  Prompting didn't work under most of the third-party terminal emulators
  on Windows because liner assumes line editing is always available.

Unlocking the accounts in the test doesn't help with anything.

rpc: several fixes and support for optional arguments

rpc: be less restrictive on the request id
rpc: improved documentation
console: upgrade web3.js to version 0.16.0
rpc: cache http connections
rpc: rename wsDomains parameter to wsOrigins

cmd/geth: add JS preload parameter

Update ethash

cmd/utils: bugfix where database is opened multiple times

console: use transaction output formatter for eth.pendingTransactions…

accounts/abi/bind: support generating bindings for various arrays

rpc: use go-winio instead of vendoring a named pipe implementation

RPC pub sub

core, miner: remove Frontier canary

abi: support for input and output slices & removed support for implicit type conversion

p2p: enable EIP-8 handshake sending

cmd/utils, miner: A/B testing JIT VM. Disabled for miners

cmd/geth: add missing gas target flag (fixing 0 convergence issue)

With the Ethereum Homestead fork is now behind us, we can
assume that everyone runs an EIP-8 capable client.