Formal release of v2.8.1

Fixed bug in initialization that affected some cases when initial moves were given.

Fixed bug that affected solutions of hands where only one trick was remaining at the time of the call.

Fixed bug in scheduler that caused some hands to be considered identical that weren't.

Added Makefiles kindly contributed by users for Linux shared libraries (as opposed to static libraries) and for Microsoft's make version.

Added Foppe Hemminga's DLL documentation written entirely in markup (.md) language.