handle play contempt mode with infinite search

[borg323]

Makes sure play contempt mode is never used inside the search, it is switched to white/black depending on the first move side, same in normal searches, flipped when pondering or disabled in infinite search. For infinite search there is a warning if contempt would have an effect. In addition there is a fix for a preexisting wdl display bug, w and l were swapped while pondering. Also some cleanups.

[Naphthalin]

I believe I tested everything which is supposed to be tested, which includes

• behaviour of go nodes, go ponder, ponderhit, go infinite, go movetime with --contempt-mode=play
• behaviour of go nodes, go ponder, ponderhit, go infinite with contempt mode white_side_analysis and black_side_analysis
• WDL sharpening active with disable
• that contempt is automatically set to 0 with disable
• warning is only printed with contempt != 0 and play
• WDL and eval display is now consistent with go ponder and ponderhit
• WDL_mu is functional with --contempt-mode=disable

I didn't find any unintended behaviour, so this is funtionally ready for merge.