Outpost Endgame values

Remove the recent rank based Outpost array by using a weighted average value
computed using a frequency analysis by rank from a large set of middle game
positions.

The higher eg values introduced by the new Outpost array (which were about
twice the previous masters) are thus preserved.

STC
http://tests.stockfishchess.org/tests/view/5dd05c870ebc5902579e1f7f
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 42466 W: 9232 L: 9151 D: 24083

LTC
http://tests.stockfishchess.org/tests/view/5dd146e342928ff08153dab1
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66968 W: 10921 L: 10873 D: 45174

Closes https://github.com/official-stockfish/Stockfish/pull/2418

Bench: 5103360