Solve trivial cases without throwing error

[jmyrberg]

E.g. if the total weight is smaller than largest knapsack, provide a trivial solution instead of throwing an error.

[AlexDuchnowski]

Similar note: In a 0-1 Single Knapsack instance, if one of the items has weight 0, it would be great to simply have it added to the solution (assuming it has a non-negative profit) rather than throwing an error.