⚖ Improve king evaluation: open and semi-open files and 'shield' bonus

[eduherminio]

• Detect open and semi-open files when there are rooks/queens in the board and give penalties to kings when they're placed there
• Measure same side pieces around the king and add a bonus for each one of them as a first approach to detect king safety

Changes in #202 and here seem to make the Lynx sharper, allowing it to reduce the number of draws in exchange of both losing and winning more games. No clear improvement regarding results, though.

Gauntlet comparing Lynx-improve-king-evaluation-699 vs Lynx-improve-pawn-evaluation-670-win-x64 vs Lynx 0.12.0.
Conditions:

• Intel(R) Xeon(R) Platinum 8272CL CPU @ 2.60GHz, 2594 Mhz, 1 Core(s), 2 Logical Processor(s)
• 2'+1''
• 2 games per encounter, 2 games per opening

Rank Name                          Elo     +/-   Games    Wins  Losses   Draws   Points   Score    Draw   White   Black 
   0 Lynx 670                       60      62     100      48      31      21     58.5   58.5%   21.0%   60.0%   57.0% 
   1 Lynx 699                       56      66     100      53      37      10     58.0   58.0%   10.0%   60.0%   56.0% 
   2 Lynx 0.12.0                    28      60     100      42      34      24     54.0   54.0%   24.0%   51.0%   57.0% 
   3 Walleye 1.6.0                 101      84      60      33      16      11     38.5   64.2%   18.3%   61.7%   66.7% 
   4 Celestial1.0                   41      83      60      29      22       9     33.5   55.8%   15.0%   60.0%   51.7% 
   5 Rustic 1.1                    -35      84      60      23      29       8     27.0   45.0%   13.3%   48.3%   41.7% 
   6 Darky 0.5d                   -101      82      60      15      32      13     21.5   35.8%   21.7%   33.3%   38.3% 
   7 Princhess 0.5.1              -301      96      60       2      44      14      9.0   15.0%   23.3%   13.3%   16.7% 

300 of 600 games finished.