Added number of winner trades

[jmoreira-valory]

Added number of winner trades per market state on trades.py summary script.
Added ROI to markets finalizing. Example:

--------------------------
Summary (per market state)
--------------------------

                        Open       Pending    Finalizing   Arbitrating        Closed         TOTAL
--------------------------------------------------------------------------------------------------
Num. trades                7            15            16             0           104           142
Winner trades              0             0             8             0            55            63
Invested            0.42 DAI      0.92 DAI      0.98 DAI      0.00 DAI      6.34 DAI      8.66 DAI
Fees                0.01 DAI      0.02 DAI      0.02 DAI      0.00 DAI      0.13 DAI      0.17 DAI
Earnings            0.00 DAI      0.00 DAI      0.96 DAI      0.00 DAI      6.25 DAI      7.21 DAI
Net earnings       -0.43 DAI     -0.94 DAI     -0.04 DAI      0.00 DAI     -0.21 DAI     -1.62 DAI
Redeemed            0.00 DAI      0.00 DAI      0.00 DAI      0.00 DAI      2.61 DAI      2.61 DAI
ROI              -102.00 %     -102.00 %       -4.17 %        0.00 %       -3.37 %      -18.72 %