An account can now approve a producer, and that producer's votes are
increased appropriately. The account can remove approval, and the votes
are decreased appropriately. Additionally, the producer is added/removed
to the account's approved producers list as desired.

TODO: A producer with more votes than the rest is still never rotated in

Calculating the new producer schedule based on votes is now implemented;
however, the voting itself is not. :D But the code builds, and the tests
pass. It's good progress, it's been a good day.

Note that "the tests pass" means little at this stage, since I haven't
written any new tests to exercise the new code. In other words, NEEDS
TESTING!

- Rename config::ProducerCount -> config::BlocksPerRound
- Add new config::VotedProducersPerRound = 20
- Split up staked_balance_objects.hpp moving ProducerVotesObject to
producer_objects.hpp

Add producer schedule changes to block_header, so light clients can see
the round changes by just watching block headers.

Implement changing the producer schedule at round changes, first checking
that the schedule changes in the block_header are correct, then applying
them.

TODO: Actually calculating the new round (right not it never changes)

Wire protocol specs say never to put an id_type on the wire, but
block_header contained the id_type for the producer which created it.
Fix this by using the AccountName of the producer's owner instead.

The producer-median-voted blockchain configuration parameters are now
updated when the round changes. The previously expected-failing test
case for this now passes

This new interface allows the chain_controller to request a fresh round
of producers and request the producers' median voted blockchain
configuration.

Net yet complete, but integrated sufficiently to get the tests to pass.

And rename it to chain_initializer_interface

Previously, we created the initial producers by manually making the
producer_object's in prepare_database. Now we create them by creating
Messages directing their creation, and invoking the normal
CreateProducer infrastructure.

Aftermath of 55a84709 -- the chain
library no longer ever touches genesis_state_type; this type is only
recognized by native_contract now, so move its files from the chain
library to the native_contract library.

Fix initial supply config constant

Add get types api

Ohh, my life would've been easier during my last commit if that rename
had actually been done rather than just commented about.

OK, so this turned out to be a **massive** refactor that I thought I'd
never finish, and no, I don't remember everything that changed here, but
I think it all worked out to be better than before, and almost all of it
was fairly necessary/the best of available options. Whew. I am SO glad
this is finally done.

High level goal: Continue refining the native contracts (ref #15),
specifically
walling off their state into their own contract DBs rather than globally
shared (read: stuff that race conditions are made of) general blockchain
state.

The first real change I made in this commit, which precipitated the
avalanche of changes that followed before the project became consistent
again, was to move the account balance out of account_object (globally
shared) to an object known only to the Eos Contract, thus eliminating
the possibility of race conditions/nondeterministic behavior.

The trouble is, balances are set at genesis. Genesis is processed by
chain_controller. chain_controller cannot know about balances, since
those are an abstraction defined on top of the Eos contract, which is an
abstraction defined on top of chain_controller. So all of genesis had to
be reimagined, and quite a lot of architectural changes had to be made
in order to create a logically consistent solution.

Changes (probably incomplete):
 - Fix up notifications within the native contract to support
precondition validation as well as application

 - Add notify handlers for CreateAccount to Eos and Staked Balance
contracts

 - Move account's liquid balance of EOS from account_object to
BalanceObject

 - Replace {producer,account}_object::id_type with AccountName most
everywhere except block_header, which still contains a
producer_object::id_type (potentially in violation of protocol
standards, but I want to confirm that before fixing it)
   - Reason: The name is not significantly slower, as it's fixed length so
no heap allocs, and it simplifies the code in quite a few places by
allowing us to look up objects directly rather than indirectly by
looking up an ID to get an intermediate object to get a handle for the
object we really wanted

 - Replace native_system_contract_plugin with native_contract library
   - Reason: The plugin was getting in the way. The native system
contract C++ implementation is simply too fundamental unless/until we
have a scripted implementation that works until the native
implementation gets installed

 - Completely reimagine genesis initialization, taking it largely out of
the hands of chain_controller and putting it in the hands of
native_contract
   - Reason: chain_controller understands relatively little about
genesis. It understands global_property_object and producer_object, but
not BalanceObject or StakedBalanceObject, etc... It also doesn't
understand the native_contract, and things like installing the native
contract, setting up accounts/balances, etc. all need to be handled by
something... native_contract is the most logical place to put it.

Sorry for the enormous commit... alas, this was the first time I got it
all building again and passing tests in days.

Fix #26 fc::variant deserialization of boost::multiprecision::number<T>

Looks good to me. Doesn't break the build on my Linux box.

Define notify handlers and require notifications be set correctly for
messages moving funds from liquid to staked and back, so balances are
tracked as they move between contracts

Create all three native contracts at genesis, and split the various
messages among them appropriately.