Improve replay_chain_database test -- make it able to collect detailed statistics about the size of blockchain databases.
ifdef out the test I accidentally enabled in the last commit
blockchain_market_order_book defaults to showing only 10 orders
wallet_market_add_collateral now takes an asset string rather than a
share_type
[hardfork] Add support for bid/ask in same trx

In the event a transaction specified a bid op and an ask op at the same
time it would fail to validate because of asset opperator += mismatch.

This will hard fork in the event that someone actually creates a
transaction that does this (ie: by using the market maker bot).

This expands the set of valid transactions, but does not invalidate past
transactions.
Speed up get_median_delegate_price() by caching list of active delegates.
Add debugging function used in wallet_tests to dump the size of databases.
When flushing the cached_level_map to the underlying level_map, write data in an leveldb::WriteBatch (hoping for improved performance)
Use const references rather than making copies when flushing
cached_level_map
Fix Mac build
Add more debug logging of pending transactions to help debug why transactions are getting 'stuck'
Added compute_item_hashes utility
Add missing file (oops)
Fix clang build