eth, eth/downloader: don't forward the DAO challenge header

eth, eth/downloader: better remote head tracking

Makefile, build: move cross compilation into ci.go

core/vm: hide ecrecover error message

Fixes #2825

Godeps: update github.com/rjeczalik/notify to f627deca7a51

Fixes #2829

node, p2p, internal: Add ability to remove peers via admin interface

Fix README typo

"fine graned" -> "fine-grained"

containers/docker: use shallow clone of single branch

eth/downloader: fix the stall checks/drops during sync

rpc: add new client, use it everywhere

eth, eth/downloader, eth/fetcher: delete eth/61 sync code

The new client implementation supports concurrent requests,
subscriptions and replaces the various ad hoc RPC clients
throughout go-ethereum.

If a batch request contained an invalid method, the server would reply
with a non-batch error response. Fix this by tracking an error for each
batch element.

The server delayed closing of connections for 3s when stopping. This was
supposed to allow for slow handlers, but it didn't really work. When
geth quits, it will just exit immediately after quitting the server.

Removing the timer makes testing easier because all connections will be
closed after Stop returns.

eth/api: rename signAndSendTransaction to sendTransaction

The eth/61 protocol was disabled in #2776, this commit removes its
message handlers and hash-chain sync logic.

containers/docker: update to alpine 3.4

eth: cancel DAO challenge on peer drop (annoying log)

Godeps: bump github.com/syndtr/goleveldb/... to ab8b5dcf104

Fix #2710 Filter race: concurrent map read and map write

cmd/bootnode: Add support for outputting a node's ID on the command line

eth: fixed chaindb upgrade

cmd, core, eth, miner, params, tests: finalize the DAO fork