Added "assemblyaihelper.cpp" and "assemblyaihelper.h"

This two files should contain a few extra functions which are helpful
for all cores. The beginning is "ensureOnePossibleMove(float ** const
vote, Gameboard board, int player)", which should ensure that the vote
array contains at least one move which is possible
Added "ensureNoIllegalMove" to assemblyaihelper.

This function deleates all votes which can't be played. After that, it
ensures that at least a single legal move is left.
Added another save guard to AssemblyAIPlayer