Improvement to static position evaluation

[divy-07]

Currently we only consider the amount of pieces on the board to rate a position. I'd like to consider the following and more factors:

• protected pieces
• piece mobility (how many squares a piece can move to)
• how many pieces of opponent we can capture
• many more

This would go in Evaluation.java

[arnavpd]

A couple more to note:
King safety: potential pins? nearby defending pieces, attacking power towards king, pawn structure relative to king

[divy-07]

Just a note in light of #26

We can also have caching for position evaluations. This would be isolated caching accessible only from the Evaluation class. (It would be static)

The caching we are implementing in #26 would, therefore, not include the static position evaluations.