Bollinger Bands Strategy with StopLoss

This is the default Bollinger Bands Strategy with a small change to support Stop Loss.
The default built-int BBS does not support Stop Loss and using it may cause large losses, specially in margin trading.

Added inputs:

• Source
  
• Stop Loss Percentage
  

릴리즈 노트:

Fixed a bug: stop loss prices were not being updated after reopening new position

릴리즈 노트:

Fixed a bug in calculating last order price