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

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

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.

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.

This completes the refactor (to a buildable/tests passing state) from my
last commit.

Rename database class to chain_controller, as this class manages
blockchain state and operations. Database was a misnomer.

Next step: make chain_controller a free-standing class, rather than
having it inherit from chainbase::database. This should give us a better
architecture, especially for testing, going forward.

The system contract C++ implementation is now in a plugin rather than
directly on database.

Note that testing_database installs this implementation on the testing
database, even though the test framework does not use appbase or appbase
plugins.

The simulated network was recursively calling push_block when
propagating blocks, which caused a lock timeout. Fix this issue by not
pushing a new block to the database that created it.

Also, replace the currently_propagating_block flag with boost's slot
blocker.

- absent signature verification

All tests now pass again. :)

Dunno what happened, but I don't have time to fix it right now.

Fix the stuff that broke in merge.

Also remove transaction_evaluation_state and the size_checker program.

- Cleaned out some cruft
- Added some new macros to remove boilerplate
- Added some more test cases

Add a testing_network class to emulate a P2P network ferrying blocks
between databases.

Add some test cases exercising databases syncing with the
testing_network and resolving forks.