Fix the attack evaluation feature

[programarivm]

It seems as if the attack evaluation is not being calculated properly when a pawn is threatening a minor piece. Attached below is the heuristic picture obtained after playing 1.e4 Nf6 2.e5.

Figure 1. 1.e4 Nf6 2.e5.

Figure 2. This is the heuristic picture obtained.

In this particular example, the Attack evaluation should be nearly 1 rather than 0 as it is plotted at this moment.

Keep it up, and happy learning and coding.

[programarivm]

Committed updates to master.