rpc: remove NotifierContextKey

rpc: move web3.js extensions to internal/web3ext

Context keys must have a unique type in order to prevent
any unintented clashes. The code used int(1) as key.

Fix it by implementing the pattern recommended by package context.

accounts/abi/bind/backends: estimate needed gas, not used

all: fix go vet warnings

whisper: deflake Test*MessageExpiration

These tests have become a common annoyance on CI. Fix them by allowing
messages with expiration == now into the cache and delaying the check
for expired message handling slightly.

Lazy "I'll just put return here instead of fixing the test" found by go vet.

logging.printf triggered a format string warning. Silence it
by renaming the function.

This fixes a few uses of unkeyed Body literals which go vet was
complaining about.

all: update license information

cmd/utils: strip excessive whitespace from api command line arguments

eth: fix single transaction tracing (run prev mutations)

eth: add chaindbProperty to debug API (+ console fixes)

This makes web3 internals like _requestManager invisible.

accounts: disable filesystem notifications on iOS

jsre: print BigNumber objects with custom constructor as number

cmd/utils: fix accounts merge error on console unlock

accounts: cache key addresses

cmd/gethrpctest: add missing chain configuration config field

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