Dockerfile: support building USB on Alpine, ignore temp files

cmd/swarm: handle SIGTERM unix signal for clean exit

Revert "params: core, core/vm, miner: 64bit gas instructions (#3514)"

This reverts commit 8b57c494.

accounts: initial support for Ledger hardware wallets

* swarm/network: integrity on incoming known chunks
* swarm/network: fix integrity check for incoming chunks
* swarm/storage: imrpoved integrity checking on chunks
* dbstore panics on corrupt chunk entry an prompts user to run cleandb
* memstore adds logging for garbage collection
* dbstore refactor item delete. correct partial deletes in Get
* cmd/swarm: added cleandb subcommand

- Handle a data race where a Ledger drops between list and open
- Prolong Ledger tx confirmation window to 30 days from 1 minute
- Simplify Ledger chainid-signature calculation and validation
- Simplify Ledger USB APDU request chunking algorithm
- Silence keystore account cache notifications for manual actions
- Only enable self derivations if wallet open succeeds

travis: split Android off OSX, use native image

cmd/abigen: parse contract name as abi identifier

closes #3650

event: use sync.Once for init for faster/cleaner locking

Signed-off-by: NDiSiqueira <dieg0@live.com>

core/genesis: add support for setting nonce in 'alloc'

event: add new Subscription type and related utilities

event: address Feed review issues

event: clarify role of NewSubscription function

event: more Feed review fixes

* take sendLock after dropping f.mu
* add constant for number of special cases

event: fix subscribing/unsubscribing while Send is blocked

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

We must take a write lock here because `GetNonce` calls
`StateDB.GetStateObject`, which mutates the DB's live set.