strategy: add support to manage ctp positions

1) add 'extra' attribute for Date.
2) upadte all methods related to positions in Futures.
3) update moveToNextTick() to support ctp.
4) update closePosition() for MarketRunStat to support
   close multiple positions in one time.
5) make ctp as a subsystem.

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>
strategy:turt1: update since positions interface changed

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>