Huge improvements to search + bugfixes

This release adds all of the standard features to search which are used by most engines, including null move, futility pruning, IID, mate distance pruning, singular extensions, and much more.

As a result, there has been a significant increase in playing strength.
The UCI protocol has now been properly implemented, so the engine should also be stable.

The topple-core2.exe file does not use POPCNT.