Added the function to calculate lot size.

A. Calculate lots by maximum loss
Invalid if "Risk %" is 0.
A stop loss must be set.

B. Calculate lots by funds
Invalid if "Funds per lot" is 0.

C. Fixed lot
The "Lots" parameter is required.

If the calculation fails in A., use B.
If the calculation fails in B., the lot in C. is used.

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In preparation.