This PR polishes the EIP 100 difficulty adjustment algorithm
to match the same mechanisms as the Homestead was implemented
to keep the code uniform. It also avoids a few memory allocs
by reusing big1 and big2, pulling it out of the common package
and into ethash.

The commit also fixes chain maker to forward the uncle hash
when creating a simulated chain (it wasn't needed until now
so we just skipped a copy there).

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".

* accounts/abi: reorganizing package and some notes and a quick correction of name.
Signed-off-by: RJ Catalano <rj@monax.io>

get rid of some imports
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: move file names
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix boolean decode function
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix for the array set and for creating a bool
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: be very very very correct
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix up error message and variable names
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: take out unnecessary argument in pack method
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: add bool unpack test and add a panic to readBool function
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix panic message
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: change from panic to basic error
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix nil to false
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fill out type regex tests and fill with the correct type for integers
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: move packNumbers into pack.go.
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: separation of the testing suite into appropriately named files.
Signed-off-by: RJ Catalano <rj@monax.io>

* account/abi: change to hex string tests.
Signed-off-by: RJ Catalano <rj@monax.io>

* account/abi: fix up rest of tests to hex
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: declare bool at the package level
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: use errors package in the error file.
Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix ugly hack and fix error type declaration.
Signed-off-by: RJ Catalano <rj@monax.io>

cmd/puppeth: fix key reuse during faucet deploys

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

whisperv5: integrate whisper and implement API

core: remove unused events

Demo of the issue: https://play.golang.org/p/EeTLFfppqC

swarm/storage: remove panic on invalid chunk

* Makefile: add make swarm command

* Makefile: minor code formatting polishes

README: change heading to "Go Ethereum"

consensus/clique: choose valid votes

eth: gracefully error if database cannot be opened

travis.yml, cmd/swarm: fix Travis CI build

core: add testcase for txpool