core/types: dependency cleanup

This removes the core/types -> leveldb dependency.

This significantly reduces the dependency closure of ethclient, which no
longer depends on core/vm as of this change.

All uses of vm.Logs are replaced by []*types.Log. NewLog is gone too,
the constructor simply returned a literal.

params is imported by leaf-ish library packages and should not pull in
the p2p stack.

build: finally settle on empty iOS ObjC package prefixes

Account management API polishes

core,cmd/utils: bugfix for ropsten dump imports

The run loop, which previously contained custom opcode executes have been
removed and has been simplified to a few checks.

Each operation consists of 4 elements: execution function, gas cost function,
stack validation function and memory size function. The execution function
implements the operation's runtime behaviour, the gas cost function implements
the operation gas costs function and greatly depends on the memory and stack,
the stack validation function validates the stack and makes sure that enough
items can be popped off and pushed on and the memory size function calculates
the memory required for the operation and returns it.

This commit also allows the EVM to go unmetered. This is helpful for offline
operations such as contract calls.

To address increasing complexity in code that handles signatures, this PR
discards all notion of "different" signature types at the library level. Both
the crypto and accounts package is reduced to only be able to produce plain
canonical secp256k1 signatures. This makes the crpyto APIs much cleaner,
simpler and harder to abuse.

cmd/utils, eth, les: bubble --fakepow flag into eth/les too

ethclient: hex encode request args for TransactionInBlock

ethclient: pass ptr when parsing eth_getTransactionByHash result

eth: fix miner start API to accept int, not hexint

rpc: remove HexBytes, HexNumber

mobile: fix ropsten chain configs

This change couldn't be automated because HexNumber was used for numbers
of all sizes.

The message now includes the index of the invalid arg.

inspect was broken by ffaf58f0 (May 2016!).
Looks like nobody uses this function.

This commit introduces a FindOnce method for filters. FindOnce finds the next block that
matches the filter and returns all matching logs from that block. If there are no further
matching logs, it returns a nil slice. This method allows callers to iterate over large
sets of logs progressively.

The changes introduce a small inefficiency relating to mipmaps: the first time a filter is
called, it acts as if all mipmaps are matched, and thus iterates several blocks near the
requested start point. This is in the interest of simplicity and avoiding duplicate mipmap
lookups each time FindOnce is called.

* whisper: refactored message processing
* whisper: final polishing
* whisper: logging updated
* whisper: moved the check, changed the default PoW
* whisper: refactoring of message queuing
* whisper: refactored parameters