dockerignore: ignore all git metadata and all tests

Tests are now included as a submodule. This should make updating easier
and removes ~60MB of JSON data from the working copy.

State tests are replaced by General State Tests, which run the same test
with multiple fork configurations.

With the new test runner, consensus tests are run as subtests by walking
json files. Many hex issues have been fixed upstream since the last
update and most custom parsing code is replaced by existing JSON hex
types. Tests can now be marked as 'expected failures', ensuring that
fixes for those tests will trigger an update to test configuration. The
new test runner also supports parallel execution and the -short flag.

As stated in the documentation, this method should be called traceBlockFromFile
and not traceBlockByFile. Previously this would result in a 'The method ... does
not exist/is not available' error.

Txpool localaccounts

Refactor downloader to use interfaces instead of callbacks

The commit reworks the transaction pool queue limitation tests
to cater for testing local accounts, also testing the nolocal flag.

In addition, it also fixes a panic if local transactions exceeded
the global queue allowance (no accounts left to drop from) and also
fixes queue eviction to operate on all accounts, not just the one
being updated.

params: remove redundant consts, disable metro on AllProtocolChanges

cmd/swarm: Exit if --ethapi is set

The previous attempt to use --ethapi as a fallback if --ens-api is not
set does not work because --ens-api has a default value, and also
setting --ens-api to "" is the suggested way to disable ENS lookups.

Signed-off-by: Lewis Marshall <lewis@lmars.net>

cmd/swarm: Support using Mainnet for resolving ENS names

Fix error when reporting numer of txs in imported blocks

core/vm: fix overflow in gas calculation formula

With this commit, core/state's access to the underlying key/value database is
mediated through an interface. Database errors are tracked in StateDB and
returned by CommitTo or the new Error method.

Motivation for this change: We can remove the light client's duplicated copy of
core/state. The light client now supports node iteration, so tracing and storage
enumeration can work with the light client (not implemented in this commit).

common/hexutil: wrap errors in json.UnmarshalTypeError

This adds type and struct field context to error messages.
Instead of "hex string of odd length" users will now see "json: cannot
unmarshal hex string of odd length into Go struct field SendTxArgs.from
of type common.Address".