Make Backtesting Usefull for stock/cfd traders

Right now cTrader allows only commisions in $ per million. Which makes it completelly useless for anything but fx trading. Stocks and cfds are never payed per millions and depend on the current stock price and purchase volume. Which means that backtesting and optimisation results are unreliable and will not corresspond to the live execution later.

Suggestion: implement ability to set commissions either % of the total amount or per lot/share for backtesting and optimisation

Initial discussion: https://ctrader.com/forum/ctrader-support/42560