Correct compiler complaints with string::npos. Delete some stupid
functions. Apply stroustrup style.
Add numbrixSolver::establishNoncandidates() to initialize list of used values
Add a stub for backtracking. Implement a successor function.
Return backtrackingAlgorithm to a stub. Thoroughly test
getNextPosition(,)
Switch back to establishCandidates over establishNoncandidates
Use an assert for checking range of candidate values
Implement a backtracking algorithm that completes the grid with unique
numbers (only need more constraints)
Implement a function that tests for contradictions