- don't store balances in ram as asset
- refactor producer pay algo to not iterate over all producers
- perform one percentage-based calculation
- partially fix unit tests
- use higher precision time

- signature checks are skipped while replaying
- abi of eosio.system contract was inconsistant, Fix #2999
- reduced console spam while syncing and replaying
- add max usage of resources when querying account

Added a unit test that would buy/sell a small amount of RAM and a large
amount of RAM.  This test showed unexpected behavior due to attempting
to sell over 2^32 RAM.  I updated the sellram action to enable selling
more than 2^32 bytes at once.

Test results show that for both large and small quantities, the user
losses a small amount of tokens and does not profit.

(cherry picked from commit 10273fa2d180f81769516b507bfdff68f06b7f87)

Add additional unit test to proof that deferred transaction with delayed authority of non-priviledged account is checked properly

removed old skeleton.abi and changed skeleton.cpp to something that will compile and can be run by cleos

Also:
* Disallow executing a proposed transaction if it has expired.
* Correct bug with return value of check_authorization (provided_delay
should not be considered in max_delay).
* Check expiration, TaPoS, and valid referenced accounts prior to other
transaction_context initializations (primarily to get more meaningful
error messages).