Remove update_budget method from flight.
Add budget_type, impression_total and impression_daily to the agent internal model.
Adds bid_amount and bid_type to the internal model.
agent prob has a 3 digits of precision.
If budget type is impression the set prob to 5% and estimate total and daily budget
Add is_capped boolean flag to agent.
Add last_imp_run field on agent used by the impression controller.
Merge branch 'even-cap'

Conflicts:
	internal/alchemy_model.py