Feature request: fractional ply level for computer opponent

[inferrna]

Imagine a situation where the level 1 ply is too easy to beat, but the level 2 ply is too difficult (since the level 2 engine is twice as smart). It would be great to have the ability to set a fractional ply between 1 and 2, allowing players to fine-tune the difficulty.

For instance, at a setting of 1.3, the base level would be 1, but for 30% of moves, the level would be 2. It can be computed like that:

current_move_lvl_ply = lvl_base + int(rand(0,1.0) < lvl_fraction);

Also related to #153

[jcarolus]

Interesting idea. I will give it some thought. Perhaps it can be combined in some way with the solution to your other issue.

[jcarolus]

Will go with solution from related issue.