FlexRebate: new IB commission plugin

Every now and then we get requests from our clients to set up an elaborate IB commission system which allows to establish very complex relationships with IBs: have up to 6 different IBs for a single account, set up different payouts based on different conditions, for different security groups and individual instruments, protect accounts from churning trades to prevent rebate fraud.

Our old Plethora plugin was not powerful enough, and we made a new system: incredibly flexible due to rule system similar to the one featured by our Ashira dealer (https://www.takeprofittech.com/ashira), and called it FlexRebate. It includes a table-like graphical program for editing plugin's IB structure in real-time — you can use it even from your work or home computer remotely, it is password-protected for extra safety.