transactions and orders as standalone events
- added transaction and order types
- moved TransactionSimulator from trading.py to tradesimulation.py
(only used by other members of the tradesimulation module)
- made transaction an independent event, like dividend

added Blotter
- flattened the transaction events to be independent
- made orders into events that reach performance (need to add
handling)
- issueing IDs to orders and tracking each transaction's order id.
- made volume share slippage fill orders independently, rather than
aggregating them into a single transaction.
- perf tracker now holds orders, serializes them with transactions.
patched minute test to use independent transaction events.