Sign of current results for branches

[rbolgaryn]

Right now, the values for i_from_ka, i_to_ka and i_hv_ka, i_lv_ka represent the absolute values and, unlike p_from_mw and q_from_mva etc., do not show the direction of the current flow. This is inconsistent with the power values. The values for the results of the current should be adjusted to have a sign.